In months past, I seemed to be able to adjust the tube temperature with the obvious and visible function on the display. For the past two weeks, for some reason, no amount of fiddling with the controls would present me with 'manual, auto' for the tube temperature. All the display would show in options was humidity level.
On a hunch, I removed the connector at the back and re-inserted it. Instantly the display showed me that tube temperature was now an option. I don't know if it was a glitch, or poor contacts at the connector, but re-seating the connector after removing it completely got me the results I needed.