A: Check the shower hose is not kinked or collapsed internally and the shower head is clear.
Check that incoming mains stopcock and any is olation valve in the feed to the unit are fully open.
Check that inlet filter in inlet to solenoid valve is clear.
Check with your supplier whether there has been any reduction in supply flow or pressure.
If all above are ok then it is likely to be the flow regulator at fault , replacement can be ordered online by clicking on this link.
http://www.showerdoc.com/shower-spares/triton/TRITO-P12120800-Triton-Stabiliser-Valve-And-Solenid-Assembly-P12120800 Answered 219 days ago | Alastair
Answered 223 days ago | LC