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Did you observe the status lights long enough for a fault display to develop? Something truly unusual is going on here...

I know you ohmed the thermostat, but DID YOU JUMPER R-W? The reservoir is OK... ok, pour some water into the pump to assure it is working. It doesn't have to actually overflow to activate cut-off...

Did you try this? Also check the low voltage wiring connections at the furnace control board. Do you have a condensate pump? Check for an overfilled reservoir and/or overflow switch circuit activated.

Do the lights blink after the initial power-up? The unit has a lot of self-diagnostic capability, and if the lights aren't blinking after a minute or so, the trouble may be in the thermostat. Try...