2009 KW T660--ISX Cummin fault codes 2637

[commonsense]

I recently had the DPF filter cleaned on my 2009 KW T660. Occasionally we get a check engine light coming on-it stays on no more than an hour-than the DPF filter light will come on and the engine light goes off. The DPF filter light stays on anywhere from a few seconds up to 40 minutes. Nothing happens to the truck when the lights come on -there is no derate in the motor.
We coded the motor and it came up 2637-fault states "Catalyst Face Plugged-Root unknown". So I think it needs to be a stationary regen but it won't go into regen.

could this just be a faulty sensor or something else???

This is a remanned ISX motor with 345,000 miles on it