New shower just wont get enough pressure ???????

[hendrixevo147]

Hi,
I am a first time user so be gentle with me : )
My old electric shower has recently broken, so I had had it replaced with a same powered more modern version, I have got a Galaxy Aqua 4000si.
My old shower although not the most powerful actually gave me hot water, however the new one never gets past the Low Pressure light, I have not had the water pressure checked yet, but I can hold my thumb over the tap and stop the flow. I am not really sure what I can now do to get my shower working.
Any suggestions would be great.
Pete

 

[gigz]

First check the stop tap has been opened all the way (then turn back quarter of a turn)