Phone Tools Blocked-Invalid Certificate

Firefox refused to connect to with the message "Your connection is not secure."   The details indicate the Cox certificate expired 11/5/18 06:54:54 am  SEC_ERROR_EXPIRED_CERT. .  I clicked on Advanced to add it as an exception, but unchecked the "Permanent" box.  This allowed me into phone tools for the current session, but after restarting my computer the error message came back.  Someone at Cox needs to update the certificate - - this could be a hack.  This started on 11/5/18 and is not a daylight savings time problem.l