Nest not providing heat

[becc930]

I had an hvac professional install the Google Nest Thermostat last night. When set to heat, only cold air would blow. However, with my existing (non-smart) thermostat, the heat does work. I do not believe I have a dual-fuel system because I do not have a heat pump,  but my home does use electric for air and gas for heat. 

The wires connected to my old thermostat are: 

W, Y, G, R, and C (black wire). there is also a blue wire in the box but it is not connected to anything (not connected to current thermostat and also not connected to any source in the attic, per the hvac professional). 

Can you confirm that this is or is not a dual system for Nest purposes, and if the lack of hot air seems to be an issue that a replacement Nest would fix? I reached out to Amazon to send a replacement device. 

Thank you! 

[CoolingWizard]

@becc930 , A duel fuel system exists when you have an heat pump (electric) and the indoor air handler is also a gas furnace (gas). When you have and air conditioner and a gas furnace you simply have a conventional HVAC a system.  Your heat is activated by your W wire.  Keep this in mind, the gas furnace has an Integrated Furnace Control (IFC).  When the thermostat calls for heat, it sends the 24V AC power arriving to thermostat on the R wire back to the IFC on the W wire. This power arriving on the W at the IFC starts the heat startup process. The IFC controls the blower fan and you should not have the Nest Thermostat controlling the blower fan. If the blower fan turns on instantly when you select heat, the nest is controlling the blower fan and that needs to be changed. 

There is a setting in the Nest Thermostat under Equipment for Heat, where you can turn on or turn off blower fan management. SETTINGS->EQUIPMENT->HEAT

AC Cooling Wizard