Your password reset link appears to be invalid.

Brand new site, no plugins, 2019 theme, and whenever I try to register a user from the front end, it sends me the “set your password” link which is invalid and leads to a “Your password reset link appears to be invalid” message.

Trying to generate a password after this (i.e. pretending I’ve lost it) also results in the same “Your password reset link appears to be invalid” message.

I’ve seen a fair few posts about this but none have found a conclusive answer. I’ve tried copying the email link, clicking on the link, and everything but making a blood sacrifice to make it work.

Any suggestions?