Password generated not working

Hi, Using PM Members Pro as membership plugin and used your plugin to import 5100 users from our mailing list- csv formatted with columns for username, email, first_name, last_name

Read that passwords would be auto generated by WP and sent in email automatically.

Opted to send emails to all new users being imported, but not existing/updated users.

The email sent showed the member’s new password, but that password is not working. We are getting a few emails each day of members reporting that they tried to login with the username and password we sent, and the passwords are not working. I tested a few of them myself and then had to reset them in the backend. Really concerned that all 5000 received passwords that don’t work. We also see about 5 emails a day of members going in and using the password retrieval tool.

Any idea how this might have happened or ideas on how we might be able to fix on our side without needing to mass email everyone a new password to try?

(some users also reported not getting the email at all, but checked with server support and looked like they sent successfully – all those users so far have either @hotmail, @comcast or @aol email addresses. They also seem to have issue with password retrieval link saying it is “not valid” when they click on it)

Primary concern is that everyone received their new login to our membership site and they are all incorrect. Any thoughts are appreciated!