This is an issue I encountered last week. Adobe's usability in this situation was so poor it didn't even return a statement to say why the issue had occurred!

Thankfully the issue has an easy fix. Download and installation of the latest Adobe Publishing Suite tools is required. This will overwrite the obsolete tool set and remove any login errors.

Why Adobe don't make these updates part of their software update is baffling, especially when it removes the ability to login and work on .folio projects and is a fundamental update to the applications capabilities.

Download the latest Adobe Folio Producer tools and find out more information.