Espressione Retro Clogged? (by 3 users)

Espressione Retro has worked beautifully for a year, but now after sitting unused for 2 months while I was away from home, very little water will come through the head when I attempt to make coffee. Tried the steam wand (to perhaps prime the pump and determine whether or not it draws water) and that seems to work as normal,. The Machine just doesn't get very much pressure of volume of water through the head. Also can't see how to remove the shower head to clean and check for clogs at that end of the system. Help?