My thermostat has a selection between gas/electric heat. Maybe switch did not select properly? Also there is a control portion of the thermostat that will only allow heat pump to work under a certain ambient temp. If temp is too low, gas is selected automatically. Efficiency controls?
Steve and Sheri with Archie (and Hiro, R.I.P.)
2000 Winnebago 35U, Ford F53/6.8l V10
F150 Ford and Vintage Aspencade.