Previously if a guest did not have, or could not recall, their password a temporary or existing password was mailed to them. That has changed.
The new process is that a 6 digit numeric PIN is emailed to the guest, and the login page changes to ask for that PIN along with the new password.
For the process to work the PIN needs to be used within 15 minutes, the 2 passwords must be the same and more than 6 characters long. Also, the email address entered must be the same as the PIN was emailed to.
If all the above is correct, then the new password is saved and the guest logged in.
When editing a guest profile the password is optional, as the guest would have had a password to access their profile. Entering a new password will reset it.