I'm locked out of my iMac

From an online article I was able to complete Apple Diagnostics and no issues were found, but I am still locked out of my iMac after I restarted it. It will not go past a page that states log-in problem, however my tracking pad can not move to any of the three suggestions offered. Plus when this originally happened several weeks ago, it went to this page mysteriously since my password had not changed. I've kept it turned off with an occasional retry at a reboot, but the results are always the same.

[Re-Titled by Moderator]