just added some plugins and error on start

[Slava]

MusicBee v3.4.7805.33382Store (Win10.0), 19 Aug 2021 14:16:

System.NullReferenceException: Object reference not set to an instance of an object.
   at MusicBeePlugin.Plugin.<ReceiveNotification>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<>c.<ThrowAsync>b__6_1(Object state)
   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()

[phred]

In order to figure out which plugin is causing the problem, disable all of them > restart MB > add them back in one at a time (which a restart after each) until you find the one that is the issue. Then post a report on the thread for that plugin.

You could also try to Installer or Portable version instead of the Store version that you're using now. I suggest the Portable, placing it in a non-Windows controlled directory (use something like C:\MusicBee.) Get the Portable version from the downloads page and then apply the latest patch from my signature.