Is this a anti cheat aka anti virus app issue, try google it, then you know why i ask this.

No thanks =)
Use google translate
https://1bx.host/stati/steam/steam-encountered-an-unexpected-error-during-startup-0x3000/

did you solved your problem?

didn't help me

maybe it will help https://www.reddit.com/r/macgaming/comments/1gl55mn/comment/lvt4hu2/

Originally posted by Kab0tyn:

maybe it will help https://www.reddit.com/r/macgaming/comments/1gl55mn/comment/lvt4hu2/

Thank you, it's worked

please help me understand where and how to enter this :)

Originally posted by ⇐⨛ЯЧС⨜⇨:

please help me understand where and how to enter this :)

Here you have it explained https://steamhost.cn/steamcommunity_com/discussions/forum/1/592891465952144378/?tscn=1741911611

I have tried everything from reinstalling clean, to checking proxies settings, the only thing is when I disabled split tunneling in IP Vanish .. I get pass the ERROR.. But when I load a game,"PoE" , I now get a authentication login error.
So until it's resolved, I'll just keep my VPN disconnected.
It seems to be the only thing that works.

Originally posted by N3gro dammus:

I have tried everything from reinstalling clean, to checking proxies settings, the only thing is when I disabled split tunneling in IP Vanish .. I get pass the ERROR.. But when I load a game,"PoE" , I now get a authentication login error.
So until it's resolved, I'll just keep my VPN disconnected.
It seems to be the only thing that works.

yesterday i was playing planet crafter ... today i get Steam encountered an unexpected error during startup (0x3000)....i did everything N3go dammus did turned off my VPN and the game started i then guit and turned my VPN on again and started my game again ..... so is the VPN the problem with the unexpected error (0x3000)...can anyone explain

Most likely your VPN is causing the error. Keep it off and see if this error pops up after it is fully off. Many games do not like VPNs as they consider them as cheating. Alot of games automatically assume using VPN's is a form of cheating in certain games. This maybe why your not having to load games up properly. Post your results on here after testing playing games for long time without vpn on. Do not turn it back on after starting game either. This will cause error probably to pop up again.