The leads to the meter may have come off. Time for a dealer trip, but a screw driver will release the monitor panel for a quick check. If there is no slack in the wire, pull gently to make some. If no movement, the wire will have to be released at the bottom of the wall. Access is under the pantry and inside the heater vent holes which must be taken apart to get to the wiring. Could also be a bad panel. I'd call your dealer service and have them walk you through a troubleshoot.
Battery should read ~13.7 on shore power. Black tank shows zero until it gets to where it shows a reading and stays there until it is higher than the next measurement point.
Travel safe. Pat