Help Please: Any Plumbers or Heating Engineers.

m_c

Sounds like a pressure issue.
The valve on the washing machine is very likely to be some kind of in-directly controlled valve (aka the solenoid doesn't directly control the main valve, it controls a much smaller valve that then unbalances the main valve causing it to open/close), and they rely on seeing a certain pressure to function correctly. Too low a pressure they'll often bypass, too high a pressure, and they just won't open.

Bellycaster

Could it be that the valve on the washer is not faulty then @m_c If so, I'm just wondering why it never leaked into the washer before. Granted, the tap fitting has changed but the water pressure will be the same.

It's odd, every time I seem to find an answer, another question emerges.