Had no idea if it was connecting to MAL correctly or not, it just always showed the login prompt. So I tried re-entering the password, disabling things like noscript, and similar but then got locked out of my account due to too many failed logins.

Needs some screenshots of the add-on itself (the prompt window) and, if it doesn't already have one, a login success notification so you know it worked. Maybe have it pop up a little message or a # next to the icon when it successfully detects and updates MAL too.