This a carrier thermostat with multiple zones and it does not have batteries. After I opened the thermostat there are 4 wires red V+, White = VG, yellow = RS+ & green = RS-. What can I do at this point?

You could check to make sure 24 volts from the transformer is getting to the base of the thermostat controler. Other than that being a multiple zone thermostat any other repairs would be best left to a professional.