I appreciate your patience with me.  Unfortunately, due to my work schedule, there has been no good time to debug over the past month.  That being said, I've updated both Windows 10 and Firefox a couple of times since I first opened the ticket, and I'm now able to log in and synchronize properly.

So, it looks like the issue has resolved itself.  Again, my apologies for leaving this hanging for so long, but it least it has a happy ending.

So, this would be a live debug session where the developer would be able to see what's happening while I perform some activities?  I hope you can understand my hesitance to open my system's security.  When would this session be scheduled (I'm on the east coast of the US)?

What is it you'd be looking to do with anydesk?

Don't know how comfortable I am with that, or how necessary.  This is what I'm seeing:

First, the login prompt:

When I hit Login, it gets to my account and says I'm online, but synchronization is not an option:

Pardon my ignorance, but what is anydesk.com?

June 20, 2021:  I'm having the same issue EverHasi reported last year.  I've added cookie exceptions for the links listed above, but I continue to only have the Login/Register buttons available, and clicking login takes me to my online account, but no sync options (again, as EverHasi captured above).

Thanks in advance.