If the heat will not come on, complete the following steps:
1. Check to make sure that the sun icon is shimmering.
2. Check to make sure that the thermostat is wired correctly, by gently pulling on each wire to ensure they are secure in their terminals.
3. Make sure the thermostat is correctly configured for the system type that the thermostat is controlling.
If these steps do not resolve the issue or you are unsure of any of the above instructions, contact an HVAC professional.