my Mira Sports max shower has stopped working, i urgently need some advice?

Please help me, my shower has stopped working the lights are still on the board and when i press the button to start the shower i get a bit of water and then the flow just stops, there is still a noise but not water. yesterday i switched off the water from the mains and on again and the shower worked, but this morning when ive gone in to have a shower it's not working again.
Please help me...