On my bike, the fan(s) don't kick in until one bar below max. There are two of them, not one. You won't see them kicking in until that point. Yesterday I would stop at a light and it would hit one below max for a bit before the fans kick in. If both fans aren't coming on it could be the sensor.
Myself, if I were testing without the benefit of the manual, I'd let it just hit max to make sure they weren't working before I became concerned. Could be a relay, could be a fuse.
You can check the fans by disconnecting them and then applying 12v external power to see if they come on.