With the machine off carefully push the left-hand side of the machine to roughly line up with the right. Then from the center pull the gantry to about the middle. If you get any resistance of any kind trying to move the gantry- look at the tube on the right to see if there is an obstruction of any kind.
On the right, there is a belt (GT2). On the back side of the machine (right side), there should be a Delrin pulley (black). is the belt still on that pulley? If not, carefully place the belt back on that pulley. On the front (still on the right side) there is another pulley but its metal. Is that still on the pulley? If both answers are yes, then the NEMA 17 on that side is not moving in sync with the other side. Keep the unit powered off and wait for support to get back with you.
If either answer to those questions is no, then the belt slipped off the pulley and that’s why one side moved before the other. After all the belts are in their proper locations. Slowly and carefully move the gantry so that the head assembly is under the camera. Close the lid and power up the unit so it can do the homing dance. After that’s done you should be good to go.