Have the exact same problem as the OP - no access to AM nor ATV+. Get the same "An Error Occurred - Try Again" when selecting "Broswe" and also get the "FUSE"-error in a popup window when trying to "Sign up" (to see whether that would lead to something).
I've noticed that creating a new "admin" account on your Mac and continue working on that one (i.s.o. your original user account) apparently seems to work for a lot of people. I however refuse to take this route (it is not a real solution but a workaround) as I have too many dependencies everywhere and nowhere.
I did try the second suggestion (killing the account-daemon, removing the ~/Library/Accounts directory, rebooting ) which did force me to re-login into my iCloud, re-add other mail accounts and what more but it didn't solve my issue either: Still no AM & no ATV+ !
I just tried de-authorizing my computer (1st attempt it return an unknown error 1001 message, 2nd attempt it succeeded) and then signing in again for Apple Music - no success either :(
For what it is worth: I have a family iCloud subscription.
There is nothing wrong with my iCloud account (it is not blocked) as I am able to access the services (ATV+, AM) on my other devices (apple TV, iPad and iPhone).
I had chat session with Apple support (Netherlands) this morning and after explaining my problem (initially the lady had me start the iMac in safe mode first but that didn't solve it - tried that one myself already but didn't want to sound stubborn) she consulted a senior colleague (after I mentioned the "FUSE"-message I got) who concluded that it wasn't my fault but that they were working pretty hard on their side to get this sorted out. In other words: They confirm it is an issue on their (Apple's) side!
Let's wait and see whether a fix will be released soon.