Welcome "Gead".... [smiley=thumbsup.gif]
As a matter of interest, can you hear the pump working when youre trying to pull a shot/flush the Group? If so, theres a good chance that the problem will lie with the 3-Way Valve (unless you meant by "Replacing the solenoid valve.", you replaced the old with a newie). It could be stuck, some detritus could be jamming the solenoid armature; or the coil could be burnt out.... :-?
Either way, unless you are a qualified, licensed sparky you will need to involve such a person in order to inspect/test the valve for you. Were not in a position to recommend unqualified people undertake these potentially hazardous tasks.... ;)