The thermocoupler should produce 25-35 millivolts when connected to the lower circuit board once it has heated. Anything less will cause either erratic gas operation or shutdown.
It is also possible that the flame failure safety valve (combo electromagnet and thermocouple switch) is not working properly. If it fails to produce 14 to 30 millivolts the electromagnet will close and shut off the gas. The internal magnet is usually the culprit and the whole unit must be replaced. If present, it is mounted to the aluminum flue collar just above the burner.
You may have both thermocouple parts if the recall was applied to your RM2652.
It may be silly to ask, but did you ensure the probe tip is properly located above the flame?