Aux/emer Heat Not Working

[DAMNYANKEE]

DUCANE MODEL# SH10B30P
Having moved to South Carolina from upstate NY, I have no experience with heat pumps. Last fall when the temp dropped to 25, I awoke to 65 in the house. The AUX light was on but the electric meter did not indicate any increase in usage. A repairman connected a tester to the coil, informed me that it tested good. He then cut the power to the unit and cranked the thermo to about 90. Waited 15 min and switched the power on, everything worked great and did so for the rest of the winter. I watched when he checked it and am resonably certain he did nothing else, except charge me $55.
About 3 wks. ago I switched from cool to heat, worked fine untill it got below 30. I cut the power, let it stand for 15 min. then cranked the thermo and flicked the switch. AUX light comes on but no noticable air temp increase and no increase in power usage. EMERGENCY mode is not producing any heat at all. Compressor is working fine.

What can I do except shell out another $55? Thanks for your time.
MRSYD