You tried disconnecting the stitch regulator?
No, try machine without regulator.
Yes, make sure you have power at the wall socket. Unplug sewing machine and plug in a lamp, radio, or vacuum to test for power. If power at wall socket, then plug sewing machine back in to wall socket. If still no power, disconnect and reconnect power cord at machine end. If still no power, try cycling the sewing machine ON/OFF switch a few times.
If still no power then likely the internal fuse or other.