Help repairing Firebox Electric Firelpace

[unmakingyou]

Hi there
I am trying to repair an electric fireplace, however I'm new to this topic. I have already checked the thermal fuse and the thermal switch and they both seem to be ok. The fireplace has an "open door" detector, meaning it is supposed to switch off if it detects a window or door is open. I think this is achieved by means of a thermistor that is mounted on its own little board. i have attached an image of the back and front of the thermistor board, and of the main circuit board, and the thermal fuse/switch. the problem is I don't know how to check if the thermistor is ok, I don't have a spec for it and I don't think there is anything on the board that gives me this information?

the issue with the electric fire is that it is not turning on at all. the continuity of the plug, the thermal fuse and thermal switch all seem ok, i checked those with a multimeter.

any help is greatly appreciated!!