Nest thermostat not heating

[Klsmith478]

I have my thermostat set to 68 at night and the past two mornings I’ve woken up to 56 degrees.  Why isn’t it kicking on at night to keep the 68 degree temp??

[Picmanbill]

Having the same issue. Thermostat is showing heat is on and fan blowing, but not getting anything at the vents