This is my first snake, I've had him since July. Male ball, 4 years old. Eats f/t and had been eating f/t for previous owner. No refusals (after the first two weeks of settling in) from July to mid October, but then suddenly stopped taking any food after the first week of October and hasn't eaten since.

His setup is great, I check the temps regularly with a heat gun and thermostat/thermometers. Ambient cool side is 79/80 and ambient warm side is 83/84. (Fluctuates a bit more as the thermostat turns the CHE on and off.) Hot spot is 88/89. He spends most of his time in the cool side.

His shed three weeks ago was perfect, and he doesn't have any sign of scale rot or an ri, and seeks perfectly healthy and the same as he was earlier. He's not lost much weight either. Cage is clean, water changed regularly, humidity I keep right around 60%+ and hasn't ever dipped below 55% since October. Water gets changed every other day and he has consistent urates and pee. (Water treated with reptisafe) Cage gets spot cleaned regularly and was totally cleaned and all substrate replaced about 3 weeks ago right after he shed. I stopped handling him for 2 months while he was on feed strike, but I've been handling occasionally now. Cage is covered with cloth for privacy and there's lots of clutter.

He seems just fine? He's energetic and occasionally goes into strike pose when the rat is in front of him. Then he just goes and pays attention to something else or wants to crawl over the tongs and up my arm.

I thaw the rats out in the fridge the day before and then warm them up with the hair dryer, same as I did before he stopped eating. I offer around 1am, when he's active. I was slightly over-feeding him when he began the strike.

Things I've tried:
-Tried the warm water defrost method too but no go.
-Leaving rat in the cage for a couple hours and putting a cloth over the cage. (I put them on a Tupperware lid so they don't get in the substrate.)
-Waiting 2 weeks between offering food.
-Putting rat on the top of the cage for 15 min before warming it up with the hair dryer. He would get out and actively look around for it when I used this method before the strike, but now he doesn't seem to care as much.
-Feeding in lower light, and once in the dark.
-Feeding different color rats.

Things I haven't tried:
-Feeding box. He's used to feeding in the enclosure, same for previous owner, who didn't use a feed box.
-Rubbing the rat with tuna.
-Feeding live.

Should I bother with trying the tuna method or a box? Or should I just go to trying live? At what point should I make a vet appointment? I'm pretty sure they're just going to say to check his enclosure temps and try a live rat.

Thanks