I have a Triton t80si shower but only getting cold water?

How can I fix this problem with just getting cold water from my brand new triton t80si shower. I have installed a new isolation switch in case this was the problem, checked my water supply that's above what is required - checked by water company. Cannot get ambient temperature when even on the hottest settings - please help as this was installed for my elderly disabled mum! Any assistance greatly appreciated.