Are you staying that you can push the gantry on the back side of the tool & it gives no resistance like the front?

Loosen and drop the X2 motor (front side @ Y0).

Pull the X1 motor off (the one on the back side of the tool) and rest it on the table. Power up the control box.

In keyboard mode (k or SK) press the right or left arrow key. Does X1 turn?

If it doesn't, then you either have a bad connection (check all wiring from motor to drive) or a faulty drive.

If yes, then hold the pinion with a gloved hand and move it again. Can you stall the motor? If no, everything is OK. If yes, then you are either running on one coil (broken wire somewhere) or the drive is flaked out.

Sometimes the connectors (Geckos) can get corroded and need to be pulled and reseated to get them up again. Does the X1 driver power LED light up?

Do you have Oriental RBK drivers or Gecko drivers? Post a pic if you are not sure.

-B