Shower not working properly some thing simple are it would not work at all

Do you know if your shower is compatible with your current system, is your system an old type with tanks in the loft or do you have a combination boiler with no tanks?

Need a bit more info on this. How old is the shower ? If newish and you are getting poor pressure it could be that the new pipework didn't get flushed and maybe bits of cuttings, rubble may of been in the system and blocking the filters. I’ve seen this before.

If the shower is electrical and not part of the hot and cold plumbing system then it could be a build up of lime scale in the heater element. This would cause the element to over heat and go in to thermal cutout briefly which would explain the symptoms you are experiencing. As for the remedy i would not like to give advice as i have always replaced showers with this problem instead of repairing them. If the shower is of a reputable brand then it would be more than possible to acquire and replace individual parts instead of purchasing the entire unit. I hope this helps.

Has the shower worked in the past, but now not work properly? If so, has anything else changed? What is the shower doing (or not doing)?