I am having the same problem and therefore unable to update my website which I tried to do on Monday 9th April. This is important as I am losing money through this. Why can't we publish our websites? Would appreciate some support.
I've done some more sleuthing and found the answer to this problem in another post called An unknown authentication error has occurred using your Adobe ID (AUTH_UNKNOWN_ERROR)
I tells you what to do. It is simple and has worked for me. Scroll down the list and check it out.
Hope that helps
Please try Deactivating and Reactivating Muse to see if this resolves the issue:
Europe, Middle East and Africa