Thermostatic Shower

Why is my shower thermostatic Geting not enough hot water?
I just had a 105he Baxi combination boiler and shower fitted with thermostatic mixer tap. even with the valve handle to set the hot water is not hot enough for a shower. all other faucets in the house are well. ideas?
It seems that neither the thermostat is faulty, the front section was not installed corectly or debris was not cleaned the pipe, that stops the flow so that the handset will not fire, heating will, should have up to 6 hours to clean the system is installed before the boiler, if not clean shower, piping, return and tell them they are lazy working environment.