Unable to Log In ("No account exists for this email. Please subscribe first.")

Page navigation wasn’t working properly — mostly-blank pages, bracketed text displayed that mentioned something about neondb — so I cleared my browser cache and attempted to log in again. After entering my email address at the Welcome Back screen, a red toaster message with the following text is shown:

Login Failed

No account exists for this email. Please subscribe first.

I’ve tried this several times. I definitely have an account and am subscribed… is this another unwanted artifact of the subscription extension for the recent downtime?