How exactly you are completing the conversion? Is it through the web browser or using desktop application Adobe Reader DC?
The Document Cloud team is aware of the issue and has been working on the resolution. There was an intermittent issue going on with the Document Cloud website while accessing the services. Which has affected few users and impacted their document cloud services (Exporting, Creating and Combing).
This issue has now been rectified and the services are up and running fine.We request you to check back whether it has resolved at your end or not.
Try with a different web browser and for testing purpose check with a different file. And do let us know if you experience the same problem.