I have a bissell proheat (by 2 users)

Does water squirt out of the hose nozzle, if it does, then check the heater inside the handle asm. Make sure that where the tubes hook up to it are not clogged. If water doesn't squirt, check for the seal at the bottom of the tank, it needs to be on the tank, not in the hole, this is for the soap bottle, there is a seal on the bottom of it as well. The flow indictor cap is leaking air or maybe is too tight. If you had the top cover off, make sure that the tubes are routed right so as not to get pinched when the cover is put back on, the smart mix knob should be in the water setting and that the piston is on the bottom of the smart mix knob. Pump is bad. Try running a mix of vinegar and water to see if that unclogs the lines. Is the top cover and the base tight together in the back, sometimes the top breaks loose and it will raise up and it can't spray, just re-fasten it down.