Symptoms

ISSUE:
When attempting to Appify a List in SharePoint, the user gets the following error:

SmartObject Server Exception: Authorization failed. User: 'AAD:user@company.com' Action: 'Publish SmartObject' . SmartObject: SharePointListName]
 

Diagnoses

DIAGNOSIS:
The ability to Publish SmartObjects is enabled for everyone by default, OOTB. However, as soon as one user is granted explicit rights, other users are denied those rights unless granted explicitly.
 

Resolution

RESOLUTION:
Granted the user rights to Publish SmartObjects by going to K2 Management, SmartObject Administration, SmartObject Security, and adding them in with Publish rights.
(Alternatively, deleting ALL entries in SmartObject security would once again open up the ability to publish SmartObjects for all users)