Hey, Jboy.
The others are pointing you in the right direction. The MP1220 will only have Hall Riser Voltage is when the controller is in Mode D (normal operation).

Perhaps the car is getting lost when you come into the bottom floor. Check your LU, LD, and DZ from the PCD. Also look at DSD and TSD. It's pretty common, even when they were new, for the contacts on the limit switches to fail to make up. Banging on the TSD might solve the problem for the remainder of the elevator's life... or 15 minutes.

If that doesn't help, the next step is to go through your manual to look up the fault counters. The counters start at E750.