Symptoms

The client reported that when opening the K2 Applify Page that they received a 'OAuth token requires authorization' Error message.
All K2 Artifacts are however loaded in the background
 

Diagnoses

This error is thrown by the K2 oauth service when attempting to issue a low trust token or use a refresh token.
This also happens when the admin password is changed and the token is still cached.
 

Resolution

Rerunning the K2 for SharePoint Registration wizard and regenerating the SmartObjects and Forms solved this issue