New ball python questions

Ok so I just picked up my first ball python yesterday. He's a male about 9 months old. His substrate is eco earth/coconut fiber and he's in a 20 gallon terrarium. He has one hide on the left and one on the right. There is lots of clutter in his tank. I have been having problems with heating. I have a medium sized eco terra heating pad attached to a jump start thermostat. The tank is a few degrees too cold. The warm side in the hide is only 26-30 and on the cold end it's only 21-22 on the surface according to my heat gun. I'm starting to worry the heat gun is wrong because the thermostat probe under the substrate says 40 but my BP refuses to use the hide on the warm side and only stays on the cool side. I tried to get him to go in the warmer hide because I was worried he hadn't seen it and was too cold but he refuses to go in and only sits on top of the hide. The humidity is about 70 btw. What is wrong with my terrarium? Any and all advice/answers are appreciated.

My normal often prefers the cool side over the warm side. Check the temperature at the surface of the glass on the bottom of the tank and then on the substrate he/she lays on inside the hide on the warm side. If the temps are right and not too hot, I’d just let him do what he wants. As long as he has access to the warm side he will go when he wants. After my normal eats he will lay in his warm hide for a day or two then he lays in the cool hide or the one I have in the middle. As long as the surface temps are good I don’t think you have anything to worry about.

I have 2 identical thermostats in my 20 gallon for the 2 UTH's. The hot side stays set at around 94 degrees and keeps the surface at 89-90. The cool side is set at 80 and it keeps the surface at 80. So I trust my temp gun not the thermostat readings. One way to test the temp gun is to aim it at the wall right next to your home thermostat. Those are typically pretty accurate. Some people fill a glass with cold water and a good amount of ice and it should read close to 32 degrees. When we brought our first BP home he would move around in the beginning from hide to hide. The last few months he has spent 90% of the time in the cools side. Are both of the hides in your tank identical? It is important to make sure the BP is choosing the cool side because of the temp and not because it doesn't like the hide on one side over the other hide.