Error all plugins
uMod Agent - (1.2.275)
games/valheim (6287700)
games/valheim (develop)
core/webclient (develop)
core/compiler (develop)
core/database (develop)

cleared the folder \umod\apps\ but no new files appeared

12:28 PM [Error] Error while compiling DataRateModifier: Compiler disconnected message was null
Compiler failed: Compiler disconnected message was null
Compiler *.*.*.* was closed unexpectedly
Compiler failed: Compiler *.*.*.* was closed unexpectedly
(Filename: C:\buildslave\unity\build\Runtime/Export/Debug/Debug.bindings.h Line: 35)

12:31 PM [Error] Failed to call hook 'IOnServerInitialized' on plugin 'Valheim v1.0.125' (NullReferenceException: Object reference not set to an instance of an object)
  at uMod.Analytics.SendPayload (System.String payload) [0x00010] in <15a7c9d83c4341f39657537d19660acc>:0
  at uMod.Analytics.Collect () [0x0006d] in <15a7c9d83c4341f39657537d19660acc>:0
  at uMod.Plugins.Decorators.ServerDecorator.IOnServerInitialized () [0x000b8] in <15a7c9d83c4341f39657537d19660acc>:0
  at (wrapper dynamic-method) System.Object.lambda_method(System.Runtime.CompilerServices.Closure,object,object[])
  at uMod.Plugins.HookMethod._Invoke (uMod.Common.IContext target, System.Object[] arguments) [0x0007f] in <15a7c9d83c4341f39657537d19660acc>:0
  at uMod.Plugins.HookMethod.Invoke (uMod.Common.IContext target, System.Object[] arguments) [0x000f1] in <15a7c9d83c4341f39657537d19660acc>:0
  at uMod.Plugins.HookDispatcher.Dispatch (uMod.Plugins.HookName hookName, System.Object[] args, uMod.Plugins.HookEvent e) [0x001b1] in <15a7c9d83c4341f39657537d19660acc>:0
  at uMod.Plugins.Plugin.CallHook (uMod.Plugins.HookName hookName, System.Object[] args, uMod.Plugins.HookEvent e) [0x00060] in <15a7c9d83c4341f39657537d19660acc>:0
(Filename: C:\buildslave\unity\build\Runtime/Export/Debug/Debug.bindings.h Line: 35)

Those errors appear to be unrelated to each other in some sense. I would say shut down the server and run "umod update valheim -P"