Add one more check. At the bottom of the handle, there may be two switches instead of the proximity switch. Make sure you here a click when the handle goes back to the raised position. If not, switch might have failed.

Without a serial number, hard to know what to check. If all you see is a picture of the handle in the display, it is telling you to let the handle up so jack can complete start up checks. If the display is still showing this, check the proximity switch at the bottom of the handle, should have a light lit on one side when you slide a piece of metal across the sensor. If the sensor lights, check all switches in the handle head, make sure none are stuck in the down position. Also, make sure the throttle is in the neutral position. Good Luck