2001 camry over heating

Thoughts - maybe the water pump isn't working right to allow enough flow pressure to pass through the thermostat? (that would suck I know, pain to replace the water pump). Also, maybe check fuses first related to the heater - you never know.

Thank you both for getting back to me. We checked the direction of the thermostat and it only goes into the housing one way so we know we have it in correctly. One thing I forgot to mention was after driving for a couple days without the thermostat in place, we then put in another thermostat. I forgot to remove the rubber gasket from the previous thermostat from the housing and put the new thermostat and new gasket in the housing on top of the gasket that was already there. So, it had a rubber gasket from the previous thermostat and second rubber gasket with the new thermostat. We were excited because it heated to operating temp and the heater blew hot; everything was working. We turned off the car and looked at the engine; coolant was pouring out of the thermostat housing. This is how and when we discovered that I forgot to remove the previous gasket. We immediately took out the extra gasket and put in the same thermostat. We started the car and it started to over heat again. I can't figure out why it would work when I made that mistake but then stop working when I corrected it.