Try and reload the group I/O through IMS. I once had a job that the config got corrupted on. In my case it was up calls, my U1 and U2 were flat out gone from the profile. Reloaded .cfg and all ran fine, but I never had a reason for why it happened. If everything is there, try injecting the call and see if the car responds, can also check the hall station and see its lit up to "prove" communication to the station, and that the CPUA still is capable of taking the command.

Edit: forgot to remind you to check OHMs over the HC. 60 is the key, and on groups there where plenty of mistakes turned over. Header jumper on the master car should be removed. When you don't have 60 the communications get really strange.