Background sync not working anymore

I dont get notifications but mails load when i open the app.

-------- beginning of crash
01-18 18:30:20.726 28897 28897 E AndroidRuntime: FATAL EXCEPTION: main
01-18 18:30:20.726 28897 28897 E AndroidRuntime: Process: com.fsck.k9, PID: 28897
01-18 18:30:20.726 28897 28897 E AndroidRuntime: java.lang.RuntimeException: Unable to start service com.fsck.k9.controller.push.PushService@9a1ac96 with null: android.app.ForegroundServiceStartNotAllowedException: Service.startForeground() not allowed due to mAllowStartForeground false: service com.fsck.k9/.controller.push.PushService
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:5286)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ActivityThread.-$$Nest$mhandleServiceArgs(Unknown Source:0)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2531)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:106)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Looper.loopOnce(Looper.java:230)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:319)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:8913)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:608)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1103)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: Caused by: android.app.ForegroundServiceStartNotAllowedException: Service.startForeground() not allowed due to mAllowStartForeground false: service com.fsck.k9/.controller.push.PushService
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ForegroundServiceStartNotAllowedException$1.createFromParcel(ForegroundServiceStartNotAllowedException.java:54)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ForegroundServiceStartNotAllowedException$1.createFromParcel(ForegroundServiceStartNotAllowedException.java:50)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.readParcelableInternal(Parcel.java:4882)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.readParcelable(Parcel.java:4864)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.createExceptionOrNull(Parcel.java:3064)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.createException(Parcel.java:3053)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.readException(Parcel.java:3036)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.os.Parcel.readException(Parcel.java:2978)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.IActivityManager$Stub$Proxy.setServiceForeground(IActivityManager.java:7214)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.Service.startForeground(Service.java:862)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at com.fsck.k9.controller.push.PushService.startForeground(PushService.kt:45)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at com.fsck.k9.controller.push.PushService.onStartCommand(PushService.kt:28)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:5268)
01-18 18:30:20.726 28897 28897 E AndroidRuntime: 	... 9 more

I forgot: There are no denied app rights in my settings

Android 14