When I tried to start the NAS on Dynamics NAV 2015 for the first time, I ran into this problem in the event log:
Server instance: DynamicsNAV80 The Microsoft Dynamics NAV Application Server session for tenant 'default' has permanently failed and will not be restarted. Reason: Type: Microsoft.Dynamics.Nav.Types.NavDatabasePasswordException SuppressMessage: False SuppressExceptionCreatedEvent: False FatalityScope: None Message: The user ID and password are not valid. Please try again. StackTrace: at Microsoft.Dynamics.Nav.Runtime.NavSession.Open(Boolean useUserPersonalization, Byte licenseToUse) at Microsoft.Dynamics.Nav.Runtime.NavApplicationServer.<RunOnceAsync>d__b.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Dynamics.Nav.Runtime.NavApplicationServer.<StartAsync>d__7.MoveNext() Source: Microsoft.Dynamics.Nav.Ncl HResult: -2146233088
It turned out that I had to change the user on my NAV service to something else the default Network Service account.