Hello, as system and networking engineer (not for IGS/505) I can help with troubleshooting networking issues you may have while trying to play Crime Boss in Multiplayer! Anything gameplay-related is here: Game Tutorial
If you have something like this:



Or "connection timeout" when trying to join someone then this guide is for you.
Will start with the more basic steps and then go to more advanced stuff. The order of these is not random, go step by step:

1. Internet connection.
   
2. Steam connection.
   
3. IPv4 vs IPv6.
   
4. Antivirus.
   
5. Firewall.
   
6. Ports and forwarding.
   
7. Router settings.
   
8. VPN.
   
9. Internet Service Provider.

One thing I want to point out is that this guide is meant to help you with troubleshooting and not to teach you about networking, so I will occasionally link to stuff if you want to get a better understanding, otherwise you can follow this without thinking too much even if you're not particularly an expert with computers, I did ask IGS to review it for good reason ;)

Generally speaking, if any of the changes bring you offline and the connection doesn't come back up for a while (it might restart after you change some parameters), simply revert the last change you've made. Don't panic! If you're not sure, ask in comments or in Support Chat[discord.com] on Crime Boss Discord[discord.com].

Yeah I know it's silly but do check your internet connection... Speedtest[www.speedtest.net] is a good place to start, if it's really really bad or almost absent, you could be having issues with that already.
Wi-fi can also be a problem and randomly disconnect you or crash, especially if you're using 5 GhZ signal, it can be temporarily turned off by port authority/military and stuff like that, I get it pretty often myself. Try to switch to a 2.4 GhZ signal and/or change your wi-fi channel, those can get kinda clogged up from nearby devices (neighbours).

Sometimes Steam will fail to login (for whatever reason, connection or even on their end during maintenances), and when that happens you will be presented with something like this:



If you check the top right, my username has been replaced by some crazy long string alongside the computer name. This means Steam login was not successful.
If this happens, close the game and open it again.

First thing is to disable IPv6, it just creates issues all over the place.
If your Internet Service Provider can't/won't disable it for you, then you can just:

1. Click on the start icon and look for "Control panel", open it.
   
2. Open Network and Internet.
   
3. Open Network and Sharing Center.
   
4. Click Change Adapter Settings.
   
5. Right-click your connection and go to Properties.
   
6. Uncheck the box next to Internet Protocol Version 6 (TCP/IPv6) to disable it.
   
7. Select OK to confirm the change.
   
8. I do recommend a reboot on this one, I rarely do it but since we are changing NIC configurations it's a good idea.

This will force your computer to disregard IPv6 and connect via IPv4 instead, which does fix quite a lot of issues already.
Disclaimer: if you have specific applications that must use IPv6, this will most likely cause them not to function properly, you can follow the steps again but check the IPv6 box to restore it.

Note: I had this problem myself.

Pretty self-explanatory, turn it off temporarily to see if it helps. Recently, AVAST had issues and started to detect Crime Boss as a virus (I would claim it's the other way around, but I digress), so if you're running a third party antivirus, please disable it and try again.
If you're paranoid and don't want to disable it even for one minute, add the program to the exceptions - you can refer to your antivirus knowledge base or support for instructions on how to do this as it's a bit different for each program.

The game works totally fine with the built-in Windows Defender software, but if you're having issues, better be safe than sorry - try to disable it as well. To do this, follow this procedure:

1. Select Start and type "Windows Security" to search for that app.
   
2. Select the Windows Security app from the search results, go to Virus & threat protection, and under Virus & threat protection settings select Manage settings.
   
3. Switch Real-time protection to Off.
   
4. Do remember to turn it back to On once we're done here, pretty please. Hard to miss as Windows will constantly give you warnings about it but still.

Incorrect firewall configuration can block outgoing connection and prevent you from playing with other people or even prevent Steam/Epic Games from logging in correctly.
This should be automatic already, the first time you start the game you will be presented with a window asking you to allow Crime Boss to connect through your firewall but we're going to check it anyway, in case you clicked on Block or something failed :D

First things first let's try to add it to the exceptions:

1. Left-click the Windows Start button and search for Control Panel.
   
2. Click System and Security
   
3. Click Windows Defender Firewall.
   
4. Click Advanced Settings.
   
5. Click Inbound Rules, then New Rule.
   
6. Select Program from the Rule Type window, then click Next.
   
7. Click Browse below This program path to select the program executable file, then click Next.
   
8. Ensure Allow the connection is selected, then click Next.
   
9. Select When to apply the rule (Domain, Private, or Public), then click Next.
   
10. Enter a Name and optional Description, then click Finish.

It should look something like this:


We can try to disable the firewall entirely if we want, although I do recommend to turn it back on later, it does matter security-wise:

1. Right-click the Windows icon on the taskbar.
   
2. Click Settings.
   
3. Click Privacy & security.
   
4. Click Windows Security.
   
5. Click Firewall & network protection.
   
6. Click Public network to examine your firewall settings.
   *The other firewalls will also be on, but the public firewall is the only one which affects your internet connection.*
   
7. If the firewall is on, the Microsoft Defender Firewall toggle will be on.
   
8. If you click the toggle, Microsoft Defender will turn off, and you’ll see a red x with a warning message.
   
9. You can easily turn it back on with the same toggle.

The game uses EOS from Epic Games to list lobbies and to have crossplay between Epic and Steam, so we will need to make sure the ports are open for those services. Very kindly, they do list them for Rocket League, so they will be the same and the procedure is as follows:

1. Click on Start and Type cmd and press Enter.
   
2. Type ipconfig and press Enter.
   
3. Take note of your Default Gateway IP address.
   
4. Open your web browser (ex. Chrome, Firefox, etc.).
   
5. Type your Default Gateway address into the URL Address bar to access your router's settings.
   
6. You may be prompted with a popup window requesting your username and password.
   
7. Most routers use "admin" as a username and "password" as a password.
   
8. You can also check this website[portforward.com] for a list of usernames and passwords. Quite often there is an actual sticker on the router itself.
   
9. Look for the Port Forwarding page once you are on your router’s configuration page. Port Triggering is not the same as Port Forwarding.
   
10. Add entries for Epic Games using the following port ranges:
    80 TCP/UDP
    443 TCP
    443 TCP
    3478 TCP/UDP
    3479 TCP/UDP
    5060 TCP/UDP
    5062 TCP/UDP
    5222 TCP
    6250 TCP/UDP
    12000-65000 TCP/UDP

Important note: port forwarding will not improve the quality of your connection to the game servers. It will only help in cases where you are unable to connect to other people or to the session browser while you are online.
Also note that routers are all a bit different from one another so the procedure may not be the exact same, I recommend looking that up on your router manual, knowledge base or even reach out to the manufacturer if unsure.

Safety note: do NOT just open all ports for everything to skip this step. It's a security risk if you do.

Source[www.epicgames.com]

Your router may have some additional settings to fiddle with, in order to open connections up.
One that comes to mind almost immediately is uPnP, you can try to turn that on if the port forwarding from previous section didn't work.
Now there's something to mention here, if you google uPnP you will find all sorts of people screaming unsafe and there are reasons for it. Basically, if you are running a business or some kind of server you don't want it to be turned on, but if you're a private at home generally you don't really care.

So, Flavio, WHY would that be unsafe? Because 10 or so years ago there were several exploits related to this protocol that allows the router to automatically map what's necessary (for ports) to connect, meaning that a DDoS attack[www.cloudflare.com] would bring your router down due to automapping all the malicious connection attempts. In which case you would just disconnect the router, connect a cable to it while keeping it offline, disable uPnP and put it back where it was. Fixed.
Now that being said, I've always used uPnP and never had a problem with any of this (and I do actually have a server at home, which has its own firewall) so once again, if you're not running a business, nobody will have any interest into bothering you at all.

Obviously, if you go to read about this on any kind of VPN provider they will absolutely SCREAM at you it's unsafe so you would buy their products. Make of this what you want.

Do not make your router admin area to be reachable from the internet, it is possible to do this if you have a dedicated IP address and turn it on (it's default OFF), but if you enable uPnP on top of it then at that point it truly is a security risk.

To turn uPnP on, you can refer to your router manual or knowledge base once again, as it changes a little for each model. Overall, it will be somewhere under advanced networking or security.

If all of the above fails, I want to try one more thing for networking and it would be a free VPN. Why? Because it can rule out connection issues simply by connecting from elsewhere. The principle behind the VPN is that you are connecting to Crime Boss via another IP address and therefore a different configuration.
I am not sponsored in any way but I can recommend ProtonVPN as a free VPN to try things out: ProtonVPN[account.protonvpn.com]
It downloads a little program that you have to run on your computer and... Look, it's honestly explained much better on their Homepage[protonvpn.com].

After you registered and got the program, run it, connect to any of its servers and then try to run Crime Boss and connect to a multiplayer lobby.
If this worked and everything else failed, check the next section.

Give them a call and let them know your connection is blocking things that it shouldn't be blocking. For instance, ask them to switch your NAT to moderate or (better) open if it isn't already, more information about it here: beautiful technical explanation[serverfault.com]

I've seen this happening, that they put some kind of firewall and the only way around it was a VPN, so trust me it can and does happen. Give them a call, it's free and they're paid to answer your concerns.