Omeka S encountered an error (login and password)

Omeka S had been installed several months ago and working well. Now, I can log into the console, but no users can log into the web application. Nor can they change their password.

When I enter a valid username and password, I get: Email or password invalid.

When I click “Forgot Password” and enter my email address, I get: Omeka S encountered an error.

Any ideas on what is wrong?

UPDATE: I am told by users that this may not have been working from the very start. Although, I know I logged in at one point, users are saying they have never been able to get it.

This issue is related to the server, not to Omeka. Check if the server can send email, or enable the log of Omeka to see the full explanation of the issue (