Symptoms

People Pickers fails to resolve user at runtime, and the error exception below is thrown:

"Thread 1: Exception has been thrown by the target of an invocation. OAuth token requires authorization. OAuth token requires authorization."

 

Diagnoses

This was due to expired admin OAuth on the customer’s Appit instance.
Appit automatically sends out a 'Token Expiration Notification' email before and after the Admin Token expires. If appears customer never received the notifications in this particular case.
 

Resolution

_1:
This was fixed by re-running the Appit registration wizard to renew the expired Admin OAuth token.
Alternatively, you can click the "Refresh Token URL" link in the email that was sent to you by K2service stating that your admin OAuth token may be expiring soon or is already expired.

_2:
You have the ability to managed and define user(s) you want to receive OAuth related notifications.
This can be self-managed under the Appit Management page i.e. K2 for SharePoint-> Management(K2 Management)-> User Management -> Roles -> OAuth Notifications, see the following screenshot for reference: http://screencast.com/t/lly6yhsm