How can I fix my Triton Shower?

I recently took my Triton Amber shower off the wall in order to re-tile the bathroom. After refitting I can no longer get hot water, even at the highest temperature setting it is only warm. What could have happened? Someone suggested that the control knobs could be incorrectly fitted but I have checked this and they are correct.
Hope someone can help.
Thanks in advance.

Alan.
January 2009