Heat stopped coming from electric fireplace.

could be batteries in the remote

One common reason for an appliance to lose heating but still function is a loss of 240 volt power. The feed could be compromised by a loose connection, or it could be an improperly installed breaker that is single phasing, possibly a half tripped double pole breaker. It could also be a fault within the appliance itself. I hope this helps.

dirty air filter, thermostat issues (dead batteries/wrong settings), tripped circuit breakers, or a lack of regular maintenance.

%100 there is no battery If the fan and lights and everything working and when turning on and only heat is cut off there is only 2 reasons, most probably is the heat safety resistor/system is broken or the elements burned out that usually can feel the smell when it stoped working

What type of thermostat is it?