title: Where do I start with POST signin-oidc errors?
body: <p>I am seeing this error in the logs quite frequently when the <code>POST /signin-oidc</code> endpoint is hit and I don't know where to start investigating it.</p>
  <p>The stack trace only reports code within the donet core library code, not something in the app code:</p>
  <pre><code>System.Exception:
     at Microsoft.AspNetCore.Authentication.RemoteAuthenticationHandler`1+&lt;HandleRequestAsync&gt;d__12.MoveNext (Microsoft.AspNetCore.Authentication, Version=3.1.23.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware+&lt;Invoke&gt;d__6.MoveNext (Microsoft.AspNetCore.Authentication, Version=3.1.23.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at Microsoft.AspNetCore.Server.IISIntegration.IISMiddleware+&lt;Invoke&gt;d__15.MoveNext (Microsoft.AspNetCore.Server.IISIntegration, Version=3.1.23.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)
     at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol+&lt;ProcessRequests&gt;d__214`1.MoveNext (Microsoft.AspNetCore.Server.Kestrel.Core, Version=3.1.23.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
  Inner exception System.Exception handled at Microsoft.AspNetCore.Authentication.RemoteAuthenticationHandler`1+&lt;HandleRequestAsync&gt;d__12.MoveNext:
  </code></pre>
  <p>The code in question is a dotnet core 3.1 web app hosted on Azure.</p>