ive just taken the top off and as you can hopefully see in the image it looks like rubber in the hole. The cap has a rubber washer in the top with what looks like was a centre bit thats missing and im guessing thats what in the hole now. should the hole just be open as in nothing inside? if thats correct is it just a case of prising that bit out and should get air/water?The reason why you don’t get air or water from it is that people tighten them too much and the rubber washer gets pushed into the the air outlet opening so in essence it’s blocked if you take it off you will see a hole in the washer and the air hole is blocked. You can unblock it but you need to be quick as the air will escape then water. Has happened a few time to me over the years theses being blocked