First pour at least a couple of quarts of water right behind and to the side of the seats at the seam between the soft top and the body. If water drains out in front of your rear wheels, then the drains are open. The little trays that catch the water are hard to see (behind the seats back in the corner with the top up) but easier to feel. There might be a leaf or some debris in there blocking the drain hole which is on the side of what I would call a plastic bump. If the drains are plugged, do a search on the UK forum for cleaning them out. Forced air might work but don't force a hard wire in there as the drain tube is somewhat fragile. Replacing the tubes is doable but somewhat involved. FYI, the CCM is on the passenger side below the drain tray. When it overflows the CCM gets a bath- not good. Don't know why Audi in their ultimate wisdom put it there instead of further back in the sidewall of the trunk, but it is what it is. I always look for dripping water in front of the rear wheels everytime I wash the car.