A user that is a Platform Manager, or has a clone of the Platform Manager role, is unable to chat in, where they had been able to before.
When they attempt to chat, they get the message 'Invalid User'.
This can be caused when a user's Blackbaud.com email does not match the E-mail field for that user on their Contact Card. Please ensure that these match, and that one was not recently changed. Restoring either email to what it had been before access was lost should correct the issue.