What should I do if I see 'Cool On' or 'Heat On' flashing on my Honeywell T6 thermostat?

When 'Cool On' or 'Heat On' is flashing on the thermostat, the built-in compressor protection feature is engaged to prevent system damage. If the compressor is restarted too soon after a shutdown, the system can be damaged, so the thermostat forces the compressor to wait a few minutes before restarting. Wait a few minutes for the system to safely restart—do not attempt to override this protection. This flashing message is also used for startup delay protection if AC power loss occurs.