I’ve figured out the problem, at some point the code that I added to the DefaultEngine.ini folder was deleted, and the AdvancedSteamSessions plugin was crashing it
[/Script/Engine.GameEngine]
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="OnlineSubsystemSteam.SteamNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")
[OnlineSubsystem]
DefaultPlatformService=Steam
[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
; If using Sessions
; bInitServerOnClient=true
[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName="OnlineSubsystemSteam.SteamNetConnection"
Here’s the generic code Epic gives if anyone is wondering.