Recently we been having issues with one user account specific in our environment, when the workflow assign a task to this specific user she receive the email but cannot interact with the task as it says (this site has not been shared with you).
This has been happening to this user only and all the others 1000+ are fine. To fix this issue I normally have to remove the user from the members group and re add her and then she is able to interact with the task.
I opened ULS Viewer and found errors in the log file regarding UPN and account not being found.
SPSecurityContext: Could not retrieve a valid windows identity for username 'domain\username' with UPN 'email@example.com'. UPN is required when Kerberos constrained delegation is used. Exception: System.ServiceModel.FaultException
1[System.ServiceModel.ExceptionDetail]: WTS0003: The caller is not authorized to access the service. (Fault Detail is equal to An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is: System.UnauthorizedAccessException: WTS0003: The caller is not authorized to access the service.1 logonOperation, Int32 pid)
at Microsoft.IdentityModel.WindowsTokenService.CallerSecurity.CheckCaller(WindowsIdentity callerIdentity)
at SyncInvokeUpnLogon(Object , Object , Object )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object inputs, Object& outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet))..
And in a separate line
No windows identity for Domain\username.
Also the Claim to Windows Token Service is started
I check AD Users and Computers and the UPN match what there, also double check the account has claim base authentication. Now every time a task comes in for this user I have to re assign permissions.
Anyone can help would be greatly appreciated.