Also getting this error:


Mods MES and RAI both work, all of the following mods fail (all tested individually):

• Reavers
  
• NPC Programming Extender
  
• NPC Defense Shield Provider
  
• NPC Weapon Upgrades
  
• Air Traffic
  
• Surface Occupation

Other mods currently enabled:

• [Mexpex] MWI - Weapon Collection 1 [WeaponCore](14)
  
• [Mexpex] MWI - Homing Weaponry (17)
  
• [MCRN] PDC Turret with retractable versions -Weapon Core
  
• WeaponCore - Replace Vanilla Weapons - MP!!!
  
• WeaponCore - 1.6(29
  
• Small and Large Block Solar Panels Pack
  
• Slope LCD Panels Mod Pack(DX11)
  
• MA WeaponCore Weapons
  
• Long-Range Ore Detectors
  
• High Tech Solar Arrays
  
• Defense Shields - v1.91(3)
  
• Critical Reactor Explosions
  
• Blast Door Sections
  
• Modular Encounters Spawner
  
• RivalAI

Dedicated server version 1.197.073

Same issue on self-hosted dedicated server
Version: 1.197.073

The only mod present is Modular Encounters Spawner ( 1521905890 )
Seems like steam is having some weird issue as well since the download is timing out... I will try unsubscribing and re-subscribing to the mod and report back.

Update 1 ( 2021 - 01 - 14 ): Unsubscribing, deleting the appropriate mod files, and re-subscribing did not affect anything. I'll go decompile the Script Loading process and see if I can figure out what "path1" is actually referring to.

Update 2 ( 2021 - 01 - 14 ): Well at least the line causing the issue was obvious:
<< string path1 = Path.Combine(path, "Data", "Scripts"); >>
When I look in my dedicated server folder the mod simply doesn't exist... it never downloaded into "%ProgramData%/SpaceEngineersDedicated/<server>/content/244850"...
which explains why the loading process fails as there is literally nothing to load.
Something in the mod download process is busted...
I know either Keen or Steam changed that process at some point as older mods are simply a compressed bin file and 'newer' mods are not compressed.
I'll try a few more things to see if I can at least get the download process working.

Update 3 ( 2021 - 01 - 14): Well unfortunately simply re-uploading the mod and downloading that didn't work either. The download simply hits a timeout;
@Keen you should probably fail to start the server if a mod fails to download.
I'm not immediately sure how to resolve this. Its possible SE DS has some setting somewhere to increase the download timeout, but I don't have time to find that atm.

Server Log

2021-01-14 09:52:57.568 - Thread: 25 -> Mod dependencies query successful
2021-01-14 09:52:57.576 - Thread: 23 -> MyWorkshop.GetItemsBlocking: getting 1 items
2021-01-14 09:52:58.069 - Thread: 25 -> Mod query successful
2021-01-14 09:53:18.110 - Thread: 25 -> Workshop item with id 1521905890 download finished. Result: k_EResultTimeout
2021-01-14 09:53:18.110 - Thread: 25 -> Workshop item with id 1521905890 download finished. Result: k_EResultTimeout
2021-01-14 09:53:18.116 - Thread: 25 -> Error during downloading: Timeout
2021-01-14 09:53:18.116 - Thread: 23 -> Up to date mod: Id = 1521905890, title = 'Modular Encounters Spawner'
2021-01-14 09:53:18.122 - Thread: 23 -> Mod download time: 20.05 seconds
2021-01-14 09:53:18.126 - Thread: 23 -> Downloading world mods - END
2021-01-14 09:53:18.135 - Thread: 23 -> Loading session: C:\ProgramData\SpaceEngineersDedicated\ZappBranagon\Saves\ModularEncountersTest
2021-01-14 09:53:18.196 - Thread: 23 -> GC Memory: 62,384,752 B
2021-01-14 09:53:18.199 - Thread: 23 -> Process Memory: 274,587,648 B
2021-01-14 09:53:18.201 - Thread: 23 -> Experimental mode: Yes
2021-01-14 09:53:18.201 - Thread: 23 -> Experimental mode reason: ExperimentalMode, EnableIngameScripts, Mods
2021-01-14 09:53:18.207 - Thread: 23 -> Console compatibility: No
2021-01-14 09:53:20.068 - Thread: 23 -> MyScriptManager.LoadData() - START
2021-01-14 09:53:20.078 - Thread: 23 -> Exception while loading world: Value cannot be null.
Parameter name: path1
2021-01-14 09:53:20.080 - Thread: 23 -> at System.IO.Path.Combine(String path1, String path2)
at VRage.Game.MyModContext.Init(ModItem modItem)
at Sandbox.Game.World.MyScriptManager.LoadData()
at Sandbox.Game.World.MySession.PrepareBaseSession(MyObjectBuilder_Checkpoint checkpoint, MyObjectBuilder_Sector sector)
at Sandbox.Game.World.MySession.Load(String sessionPath, MyObjectBuilder_Checkpoint checkpoint, UInt64 checkpointSizeInBytes, Boolean saveLastStates, Boolean allowXml)
at Sandbox.Game.World.MySessionLoader.LoadDedicatedSession(String sessionPath, CancelToken cancelToken, Action afterLoad)
at Sandbox.MySandboxGame.InitQuickLaunch()
2021-01-14 09:53:20.080 - Thread: 23 -> MySandboxGame.Initialize() - END

I switched from the Keen server launcher to Torch and it worked right away