No display in thermostat. Checked breakers for furnace and AC. Reset furnace/AC unit. What next?r

Could be a number of things. Does your thermostat have a battery? It could be a bad battery. It could be a bad control board, it could be a bad low voltage transformer, it could be the fuse on the control board. The board is inside the air handler section of the heater. If you remove the front of the heater, you should see a small red or green diode light. It may be a steady light or a slow flash, depends on your model. If there is no light, look for the fuse, like one in your car, on the board and replace it, typically 5 AMP.

As ms0641 said, check if you have power in your thermostat. If your system is anything like mine your stat gets it power from a 110V circuit via Xformer separate from the 208V system powering your AC. Your AC is protected by a ckt. Breaker and a fused disconnect. Check that you power at the disconnect. But your problem may just the stat which is inexpensive to replace.