There has been an issue with sprintr and logins to the teamserver. At my end it seemed to be solved so you might try again to see if it now works again.
getting similar problem in last hour running
Internal Server Error
An unexpected exception occurred while handling request callback
Current status: problem resolved itself, presumably from the Mendix server side of things.
In brief: the next day the symptom changed from Internal Server Error to merely hanging indefinitely when publishing.
After some time the publish button stated working.
More detail about this at: https://support.mendix.com/hc/en-us/requests/85468?page=1