Hi, Welcome to Just Answer, I can help you with this.
Were there any INACTIVE codes with this ACTIVE code. Reason why I am asking is because the inactive codes can tell us why its not regening properly.
If the Inlet temps are not coming up, there are a few reasons.
The intake throttle valve closes so that the engine can heat up the exhaust enough to start the regen. If it does not close, it will not heat up.
You could have exhaust leaks in front of the Aftertreatment device.
The doser injector nozzle could be plugged up, or there is low fuel pressure to the nozzle.
Usually when I see this problem, you will get a Doser fuel supply pressure low or HIGH fault code INACTIVE in the list. Plugged fuel filters are the primary cause of this.
If the engine does not heat up due to bad thermostats, it will abort the regen also.