Hey u/Rivalistic, I'm sorry to hear you're experiencing this issue. Been helping you guys out behind the scenes and this seems to be a widespread concern that's stemming from a few web related hiccups.
The most common issue we're seeing during the migration is what u/Saltrenis pointed out - the known login issue with uppercase letters for some users. For now use all lowercase letters when logging into the website or launcher. Alternatively we have people coming back who have forgotten their passwords or login details. This will usually generate a "Password Invalid" message if the password is incorrect, or a "Username Invalid" message if likewise, the username is wrong.
Unfortunately the self service account recovery functionality has not been enabled at this point. Attempting to prompt a password reset will generate the "email is invalid" message but rest assured that's just because the functionality is offline, your email is valid and fine! A recent announcement was made that all account recovery functionality is scheduled to be online soon. This of course is all pending a patch from our very swamped and very stressed web dev team haha.
We truly appreciate your guys patience and understanding in the meantime! If you've tried these first pass resolutions and are still experiencing an issue, shoot me a ticket via the "support" button on the website. There are some niche but more advance issues that some players will need GM assistance for.