CM 871 Code 2639, DPF won't clean

[Doops22]

I've got a CM871 ISX and the driver hit the regen switch to "stop", so it has been skipping regens. It got plugged up and derated, and he limped it back to the shop. I've been doing stationary regens and now have code 2639 active for DPF plugged and the dpf light is on solid, so quickserve tells me this means it is at level one (lowest level plugged) and the only action needed is a stationary regen. I've done 5 stationary regens and this code still won't clear. The only other code I am getting is 2215 for low fuel pressure. The only symptom i've noticed with that is hard starts. Could that affect the regen at all? Should I just keep doing stationary regens until it clears or try something else? I have a Cummins Quickcheck code reader but no insite to see data.