so far it sounds like the motorized auger is not feeding pellets reliably to the burner pot. And that when the pellets in the pot are burned out, the fire goes out. Is that an accurate statement?
So far it sounds like it might be a printed circuit defect.
Next please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.
You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here.,Include a picture of the thermostat wire connections to the printed circuit board in the same area.
If you have an error code showing, tell me what the code read out is on the wiring diagram or a sticker next to the diagram please.
If there is no paper clip-icon, look for the '+attach files' link at left of your send button.
I can mark it up with trouble shooting instructions.
Tell me a lot about your technical skills background and if you have a multi meter or not so that I can coach you most effectively. If none of those skills are in your bag of tricks, tell me which direction you are from the center of the nearest town or city and I will see if I can find a well rated service outfit for you.