When signing up (at least through Google Chrome), Readlang’s credentials get saved to the password manager as a Name-Password pair instead of Email-Password. The login screen then gets auto filled with a name and a password, and it doesn’t let you in, as it only accepts emails as a login name, not names.
Solution: Let the website use a name as a login credential or make password managers stop recognizing the name field as something they need to save and make them save an email instead.