Thermostat issues. Will not kick on when heat needed

first what system is in house or apt --is this a multi zoned --multi stage system is your stat even hooked up --what is the knob hooked up to ---you can change stat but if it doesnt control anything why change something thats not doing anything you need to get a meter and test and find out what controls the system and what type of system [s] you have

Expose the wires and carefully put the yellow wire in with the red. See if outdoor unit kicks on.

relay module and t-stat issue with communication cable.

SHUT THE POWER OFF TO THE FURNACE, REMOVE THE THERMOSTAT FROM THE THERMOSTAT SUB BASE TAKE THE WIRE THAT IS ON THE R TERMINAL AND THE WIRE THAT IS ON THE W TERMINAL AND CONNECT THEM. TURN THE POWER BACK ON. IF THE FURNACE COMES ON AND WORKS FINE THEN ITS IN THE THERMOSTAT.

If the temperature doesn't drop when the air conditioning is running for some time (two hours), the air conditioner is not working. The problem is not in the thermostat.
Gary

usually this is a bad thermostat, no signal to furnace. have a great day!! if not the furnace its the thermostat not turning furnace blower on.

change your thermostat that could the issue

What are you setting the thermostat to when you turn on the AC , if you turn on the AC and the house is warm you will need to turn the AC down to a lower setting before the the AC will start up.

sounds like the thermostat replaceing it should help you could try cleaning the old one they can get dust it them

Did you recently replace the thermostat? If so you need a thermostat for electric heat. This thermostat will turn the blower on when the heat is calling.