are you using some kind of backup software to run Muse from?
What I think the ACP is trying to ask is if you have any of your files or extensions on a remote location?
Meanwhile, I am asking around to see if anyone in the team has an idea. I don't remember seeing a similar error previously on the forums.
For quick help and investigation, I suggest getting in touch with Adobe Customer Care Contact Customer Care directly. I request you to post the solution here after your issue has been resolved.
I would like to take an opportunity for looking into your issue, and surely will guide you with the best possible solution.
Could you please answer to the below questions before we proceed so I can drill down into the issue?