The root cause of this issue has not been entirely determined.
However, the problem is usually seen after users were able to login previously. Normally the causes are:
- A problem in the browser's cache.
- Changes to the Organizations authentication method.
- Changes to the User object.
- Users at times create trial accounts, then may face this issue upon being invited to a corporate organization.
- Users are created in Flowdock, but not in Agile Central, then they are added to Agile Central yet the Flowdock's Organization's authentication requires authenticating via Agile Central.
- For Organizations that require authentication using Agile Central, this will happen if the username is disabled in Agile Central.
- Flowdock usernames are case-sensitive while Agile Central usernames are not.