Connection failure

A couple of weeks back, my wifes MBP decided it would not connect to iCloud Mail. She gets the message window: Mail can't connect to the account ... Enter the password for user ... Entering the password fails.

I looked at her preferences, which are similar to mine (except for the username, etc.), hoping there would be a solution. Nope. Also, in the preferences pane under Account Information, she has an extra section titled TLS Certificate, which is not present in my pane, and which has None selected.

Any suggestions to getting her Mail back online?