Sudden "Wrong Password" problem

A friend of mine crashed mid-dungeon, and when he tried reloading he was told his password was incorrect.
After a few attempts to make sure he wasn't fat fingering something or caps lock was on or some such, he clicked "forgot password?" to reset it.
And he never got the email.
Checked spam, checked other email addresses, all that. Nothing.
He tried the reset again. And again. And again. Nothing.
He restarted the launcher.
He restarted steam.
He restarted his computer.
He uninstalled and reinstalled the game.
He tried again over multiple days.
He tried again after the recent maintenance.
Nothing has worked. Password still inconceivably wrong. Email still nowhere to be seen.
I sent a report from in game, in case his account was the problem, and now I haven't gotten a response in 3 days.
I thought about seeing if he could log in on my machine, but I'm worried that would cause whatever issue he's having to 'infect' it.

Please, what needs to happen to just fix the password problem?