If the thermostat is fine, the circuit breaker is on, there is electricity to the house and the AC doesn't work; the heating doesn't work - what's the problem?
Glancing into the return in the hallway might lend a clue.
We have many years of dust build up.
Now, people think this is because they don't use a good air filter in the HVAC unit, or replace/clean it enough, or whatever.
The problem in this photo is from general dustiness in the house. If the house isn't vacuumed often, or dusted, dust happens and the dust floats easily. Of course it will move with air and if air is being sucked into the HVAC returns the dust will accumulate over time.
Dustiness in the house has little to do with the HVAC filter!
LOOKING INTO THIS RETURN, THE ACCUMULATED BUILD UP IS FROM MANY, MANY YEARS OF GENERAL DUSTINESS!
When you see this kind of build up keep in mind, it is not simply "dust." It also contains millions, billions probably, of living organisms.
What did I expect to find inside the HVAC unit, in this case a heat pump?
More of the same!
Predictably this filter (the washable kind) was so clogged the screen had been getting pulled into the unit.
The electric panel board and the blower inside were similarly caked with dust.
The house is 29 years old. This is the "replacement" heat pump and is only six years old!
I really don't know how long a heat pump can last without a filter being changed, but could this filter have six years worth of dusty build up?
In the past I have seen the cheap, cardboard filters so caked and the unit actually tried so hard to get air that it collapsed the filter right into the blower! Not in this case however. This filter has a plastic frame and isn't that easy to collapse.
One of my (silly) jokes that I grace clients with on home inspections is, "How often once a month should you replace or clean your filter?"
WOULD IT SURPRISE YOU THAT VERY FEW GET IT AND ANSWER "EVERY SIX MONTHS?" OR "ONCE A YEAR?"
There might be a month here and there when the system isn't used much and the filter does not need replacement. But once a month is a great rule of thumb!
My recommendation: while my joke may seem silly, it is intended to be instructive. Clients don't forget it! Truly, not cleaning the house and not replacing/cleaning the filter can be an HVAC system killer! Then, when the system doesn't fire up during a home inspection, the inspector won't have to say, "I think it died from choking on dust! It needs to be looked at by a licensed professional..." Well, that guy is in for a good pay day!