The Apple Books No-Login Loop

I am unable to sign into iTunes connect to publish a book. I sign in to Apple books for authors. Click "Sign in to iTunes Connect" > hit "Continue" > "Submit a New Book" ; the "Continue" button remains grey, and I am kicked back to the previous page. Repeat.

It is the same issue as this person: Caught in a loop trying to create an Itun… - Apple Community

The same issue as this person: https://discussions.apple.com/thread/250211186

And their "solution" DOES NOT WORK. Apple, this is an issue that I and apparently plenty of others have had for going on 5 YEARS. How can you think that is acceptable?

You claim to make this process easy, yet I have to post a question here to figure out how to do something as simple as sign in. You try all you can to be seamless, but your best response is "ask the Genius bar." A solution that requres going somewhere else is not seamless. You are a "tech company," but your websites don't work. Now the real question is, am I going to be shouting into a void, or are you actually going to help me? Because that, too, seems rare on the Apple Community boards. Better than Microsoft's..... but that ain't saying much.