I had the same problem. It turned out to be the flexible pipe. There was an inbuilt valve in it that had blocked
John Bates, September 2009
Sounds like the inlet valve washer has adhered to the seating so stoping water inlet.
Depends on type but plastic ball valves have a large diaprham washer and it's probably stuck to the seating.
Turn off the water to cistern remove the float arm undo the large nut on the valve assembly and see if the washer has stuck. Pull it off get a replacement re-assemble.
