In one bay, or all bays? Continuous or intermittent problem?
One bay = probably problem found in the meter box with bad rotary switch, loose wire, etc This is the most likely culprit. Or possibly a check valve in the boom manifold has failed to open.
All bays= systemic problem, which will be probably found in the equipment room. Loosing air in addition to liquid pressure indicates it's probably not the pump, float switch, tank level, or controller. It could be the solenoid got disconnected during some work.
