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?