Apple TV+ Web Login: Can't enter email before email/AppleID box disappears

On the web (using Chrome or Firefox), when I go to tv.apple.com and click "Sign in," the sign-in dialog box pops up with a field to enter "Email or Apple ID".

That field then IMMEDIATELY disappearsr, with the popup resizing itself as though that field alone never existed.

I have disabled all popup/ad blocker extensions, and the behavior persists.

As of now, I cannot watch any AppleTV+ shows on the web.