CJ wrote:
I have a gas fired hot air heating system. The pilot stays on but the
burner never fires when the thermostat is turned up above the current
room temperature.

What should I look first?

CJ

Probably in the Yellow Pages for heating service, or your gas company.
Seriously.

Could be anything from a closed valve, to a thermostat/wiring problem,
to a stuck solenoid valve.

Probably time for regular service, anyhow.

HTH,
J