Users are blocked out after being added to the atlassian-addons group.

This group is not meant to grant any permissions, and is intended for use only with Atlassian Connect. Installing an Atlassian Connect add-on creates a user, who is added to this group automatically. This user's permissions, together with the scopes white list determine which API calls an add-on can make.

Users should not be able to add anyone to this group, and right now it's completely blocking people from logging in if they are added.

Workaround: Remove users from the atlassian-addons group.