First thing to try is to sharply bang the flap just above the left Audi ring ( from the front ) this may fully seat the catch so that it will release. Get someone to help you. While one person pulls the handle firmly but not too hard, the second push the flap towards the engine then try to open it. If that fails you can insert a long thin screwdriver above the join between the left and second left Audi ring and gently push the flap towards the right headlight. This is usually enough to unlatch the flap. Once open you may want to adjust the catch or lock positions.