i have just recently built a pub shed, everything is amazing lager is working perfectly (until it runs out and I have to buy another keg!) apart from my Guinness. When we had the opening day the Guinness was OK, it poured a bit quick but it looked like a normal pint of Guinness and was fine all day and night. The next time I came up to the pub (shed) to pour a pint of Guinness about 5-6 days later it poured just black, flat and no head whatsoever. I’ve messed around with the regulator and cleaned the lines but it is still the same just coming out really quick with no head at all. I am a complete novice at this so would really appreciate any advice to solve this issue.