The temperature in my Hansgrohe Thermo Balance shower is always the same, no matter which way I turn the knob. It's generally warm enough to shower, but I cannot adjust it neither hotter nor colder. It uses a push-and-turn mechanism to adjust. The temperature adjustment is working correctly for all the other sinks and showers in my house. I tried adjusting the maximum temperature on the cartridge, but that had no effect. Do I need a new cartridge or am I overlooking something?
Thermostatic controllers typically become calcified over time. This can result in the temperature not setting properly when you adjust it or even vibration and/or knocking in the valve. Sometimes just turning the knob rapidly several times from stop to stop will loosen things up. The manufacturer also provides videos on cleaning the valve which you should try if you haven't done it.
If none of this works you'll probably have to replace the cartridge which is a fairly simple procedure if you're handy at all.