Tajima C1501 - Keeps beeping PLEASE HELP...

Hi, I have a tajima TEHX c1501 and it keeps beeping. The control panel LCD reads THEX... and does not go further. This occurred after my thread got stuck. Sounds like a system crash, but don't know how to reset. It is not my emergency button. Needle position is incorrect too after lining up the red line (knob behind the machine). What can be wrong? Any tips will help. Thank you! Keith