The (OnlineSubsytem or OnlineSubsitemUtils or OnlineSubsytemEOS) Configuration… Online Subsystem is being replaced by Online Services
I had a couple of crashes and I had to reinstall the plugins… and it worked
Online Services
The Online Services plugins have not been tested in shipping titles. As of UE 5.1, the Online Services plugins are an API-complete version for developers to use with the intention that they will be shipping on a future version of the engine. We also recommend using Online Services for developers targeting their own backend, or those who will be incorporating a number of UE upgrades beyond 5.1 into their project before shipping.
Online Subsystem
Use the Online Subsystem for any title shipping in the near future, or when you do not plan to incorporate any engine upgrades beyond UE 5.1 into the project.
And probably some of this configuration (DefaultEngine.ini) has stopped working
[OnlineSubsystem]
DefaultPlatformService=EOS[OnlineSubsystemEOS]
bEnabled=false[/Script/OnlineSubsystemUtils.OnlineEngineInterfaceImpl]
!CompatibleUniqueNetIdTypes=ClearArray
+CompatibleUniqueNetIdTypes=EOS[/Script/OnlineSubsystemEOS.EOSSettings]
…
…[/Script/Engine.Engine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName=“GameNetDriver”,DriverClassName=“OnlineSubsystemEOS.NetDriverEOS”,DriverClassNameFallback=“OnlineSubsystemUtils.IpNetDriver”)[/Script/OnlineSubsystemEOS.NetDriverEOS]
bIsUsingP2PSockets=true