PC2A Meter Not Responding

For some strange reason, there's one buss where I have inserted the PC2A module and the gain reduction meter doesn't respond no matter how much GR I apply!? Another PC2A works fine on another buss. I tried removing and reinserting the module and still no luck. I changed the position too and still the same. It's getting a signal because the LED is flashing. Has anyone else seen this behavior? I'm running X2a.