Symptoms
After removing appit from all site collections the ability to run the registration wizard was lost. It would error when trying to register the SharePoint Service Broker:
SmartObject Server Exception: Authorization failed User: K2SQL:[KUID] Action:Publish SmartObject SmartObject [Site]
Diagnoses
The error indicates that prior to removing Appit a User and/or Group was added to the SmartObject rights which has subsequently disallowed that K2SQL account the rights it needs to create SmartObjects.
Resolution
Navigate to https://[KUID].appit.com/management/ and add that account to the SmartObject Security rights granting it publish/delete rights.