TinyCat: Patrons getting error message when trying to log in

I have patrons reporting that when they go to the login section of our library's TinyCat homepage, they receive the message "Patron Accounts are disabled for this library". We have a paid account with the Full Circulation option enabled.

It seems to be inconsistent: some patrons say it works intermittently, some say they've never encountered a problem, and some say they've never been able to log in.

I have been able to reproduce this bug using Chrome on an iPhone: I am consistently getting the "Patron Accounts are disabled for this library" error. Using Safari, I received the error message once, but after reloading the page, I have been able to log in normally.