"Sign in with Google" stops working when the establisher ceases to have administrative access in Google Apps

At present, if the person who established the link between Google Apps and Atlassian Cloud has their administrative rights revoked then the link will break. This should not need to be the case as users will leave the company, or role, or may only have temporary rights so that they can establish the link.

This can lead to a confusing situation for many customers when Google Apps just suddenly stops working.

Workaround

Follow the guide https://confluence.atlassian.com/display/CLOUDKB/Google+Apps+users+experiencing+%27Unexpected+error+in+the+authentication+system%27+when+logging+in for potential workarounds.