You probably do not have the connector block pushed fully home. If you can't fold the cover flap over the block, then this is why. It does not leak in service.
If the O rings are dry , it is very difficult to push the connector on fully. Put a smear of lubricant on the little tube in the socket, and also over the 2 o rings on the block. (But not WD40). If you still have problems get the correct o rings from a dealer (in case it has the wrong size fitted) - they are quite a narrow cross section, and best changed each season. Keep spares as well