Question Unity Mediation causes an error

I tried to stitch to Unity mediation from the legacy ads because that didn't show any ads. But after switching to Advertisement with mediation this error is shown. Can you help please? I removed the scripts for the ads entirely.

Stopped polling job due to exception: System.NullReferenceException: Object reference not set to an instance of an object
at GooglePlayServices.UnityCompat.VersionFromAndroidSDKVersionsEnum (System.String enumName, System.String fallbackPrefKey, System.Int32 fallbackValue) [0x00001] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.UnityCompat.GetAndroidTargetSDKVersion () [0x00036] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver.CanEnableJetifierOrPromptUser (System.String titlePrefix) [0x000b0] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver.ResolveUnsafe (System.Action`1[T] resolutionComplete, System.Boolean forceResolution, System.Boolean isAutoResolveJob, System.Boolean closeWindowOnCompletion) [0x00014] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver+<>c__DisplayClass102_0.<ScheduleResolve>b__1 () [0x0001f] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver.ExecuteNextResolveJob () [0x00073] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver.ScheduleResolve (System.Boolean forceResolution, System.Boolean closeWindowOnCompletion, System.Action`1[T] resolutionCompleteWithResult, System.Boolean isAutoResolveJob) [0x000ac] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver.AutoResolve (System.Action resolutionComplete) [0x00018] in <48abf529805a49c69e88ffb3f8b573e9>:0
at GooglePlayServices.PlayServicesResolver+<>c.<ScheduleAutoResolve>b__78_1 () [0x00024] in <48abf529805a49c69e88ffb3f8b573e9>:0
at Google.RunOnMainThread.ExecutePollingJobs () [0x00052] in <ac8e755fbc27434ebdaf117e2c7041d9>:0
0x00007ff61d3df07d (Unity) StackWalker::GetCurrentCallstack
0x00007ff61d3e5d59 (Unity) StackWalker::ShowCallstack
0x00007ff61e3555f3 (Unity) GetStacktrace
0x00007ff61e9ecbfd (Unity) DebugStringToFile
0x00007ff61c55f482 (Unity) DebugLogHandler_CUSTOM_Internal_Log
0x0000025eedce3e23 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
0x0000025eedce3d3b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
0x0000025eedce3a80 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
0x0000025eedce3945 (Mono JIT Code) UnityEngine.Debug:LogError (object)
0x0000025dfe59810b (Mono JIT Code) Google.RunOnMainThread:ExecutePollingJobs ()
0x0000025dfe5977eb (Mono JIT Code) Google.RunOnMainThread/<>c:<ExecuteAll>b__24_0 ()
0x0000025dfe597716 (Mono JIT Code) Google.RunOnMainThread:RunAction (System.Action)
0x0000025dfe597653 (Mono JIT Code) Google.RunOnMainThread:ExecuteAll ()
0x0000025eedc7a170 (Mono JIT Code) UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()
0x0000025f15871cb5 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void (object,intptr,intptr,intptr)
0x00007ff9b6cffe24 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
0x00007ff9b6c3e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
0x00007ff9b6c3e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
0x00007ff61d303354 (Unity) scripting_method_invoke
0x00007ff61d2e2be4 (Unity) ScriptingInvocation::Invoke
0x00007ff61d2dd7f5 (Unity) ScriptingInvocation::Invoke<void>
0x00007ff61d43448b (Unity) Scripting::UnityEditor::EditorApplicationProxy::Internal_CallUpdateFunctions
0x00007ff61dd5daf2 (Unity) SceneTracker::Update
0x00007ff61df0d84a (Unity) Application::TickTimer
0x00007ff61e35b78a (Unity) MainMessageLoop
0x00007ff61e36003b (Unity) WinMain
0x00007ff61f6e64ae (Unity) __scrt_common_main_seh
0x00007ffa27f67034 (KERNEL32) BaseThreadInitThunk
0x00007ffa294426a1 (ntdll) RtlUserThreadStart

 

Hi @DeclanMcPartlin, I started having the issue with 2021.3.8f1. I updated to 2021.3.12f1 then to 2021.3.13f1 but the problem stayed. I tried a lot of things. Deleted the mobile dependency manager which came with unity's advertisements with mediation and installed external dependency manager. After forcing resolve the error simply changed to "failed". I did this with the help of a programmer and he said it can't find JAVA_HOME but we tried to resolve that too and the error persists.

I'm thinking of copying everything that I put into the project into a new empty project because maybe I deleted something along the way that I shouldn't have.