If a user sees a 520 error after trying to log in with a newly created account, it’s usually caused by one of two things:
Inactive account
If the account hasn’t been activated, the system will block login attempts with a 520 error.
To fix this:
Go to Administration, then click on Users.
Search for the user.
Click Edit.
At the top of the page, select Set User as Active.
Email security blocking password reset
Some email system scan incoming messages, which can invalidate the password reset link before the user sees it.
To fix this:
Change the user’s email to a personal one (e.g. Gmail)
Send the password reset email again.
Have the user reset their password and log in.
Once successful, switch the email back to their work address.