I have a number of RUT240's where I can't see the temperature reading in rms. It is just displayed as "-" (see screenshot).
I have 1 unit where the temperature is indeed displayed. All running the same same firmware version: RUT2_R_00.07.01.2
I see other posts suggesting a re-flash of the firmware, but that would be my very last resort, as these routers need to onlline, and are hard too access physically, if something goes wrong in the flashing.