I have a master tent 400 heater we replace a thermal regulator. The heater was coming on, but then shutting off after replacing the thermal regulator heater came on and ran like a champ. About four days later the heater would not heat above 65° so I went out and replaced the high limit switch, turn the heater on fired up heat the spa to 104° couple days later the homeowner says now it still won’t go above 65° all of a sudden so we went out as per recommendation from my old boss. I’m doing the work for him he’s furniture me with the parts Stack sensor turn the heater on heater start it up heat the pool to 95° stop will not go above 95° pool and spa mode on the heater set in the set to 104. I’m almost at a loss it also has not thrown any type of codes on the back of the board , just like this morning when I went out there, none of those LEDs were lit up no codes whatsoever. Every other time none of the LEDs were lit up. Could be something basic as temperature sensor into the piping for the touch.