Valve Issues
Greetings & welcome. Not sure what type of valve it is, but if the air is coming straight back out again, as opposed to leaking out once you have some pressure in it, I would guess that the centre post of the valve is pushed in and turned, keeping it 'open'.
Have you tried pushing the centre of the valve in and turning it a quarter until it 'pops' out a little bit? (sometimes the spring holding it in is quite strong though).
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