I'm having this same issue! its super frustrating as I've been trying to show a client his sample site since yesterday morning! I've tried restarting muse, restarting my Mac and haven't had any luck.
I have the same problem. I changed back to version 2017, but there is no change.
BusinessCatalyst is maintenance.
”This feature is currently disabled due to scheduled system maintenance. Please try again later.”
Can you try solution two (clean up cached user log in information) in the following doc and let us know if that helped? You will have to sign back into Creative Cloud after you are done.
That doesn't work!