Your tub doesn't have a timer. It is designed to set the temp and leave it there, at all times. If it is not getting hot enough, check a couple of things;
Be sure the filter(s) is(are) clean. Don't JUST rinse them, use a 'filter cleaning' solution.
Be sure the "Summer Timer" is not on. If you see an icon which looks like a clockface and a sun, your summer timer is on - that actually shuts OFF the heat for eight hours per day, and you don't want that unless you are in a heat wave and the tub is running above your set point.
Finally, your thermostat system may be off a degree or two. If you set the tub at 101, and it's holding the same temperature all the time, but that temp is only 99, the tub will feel cool. Try setting the temp a degree warmer, and see if you like that. Again, go one degree at a time, and leave the setting alone once you find the setting you like. If you have to have it set at 103 so it is comfortable, that's fine! It doesn't matter if a setting of 103 actually gets you a real-life temperature of 101 or whatever.
