If the poppet on your keg is faulty, it is relatively simple to replace.
If you're unsure if this poppet will work with your keg, try the 'Universal Poppet'.
Three Piece Airlock
Cascade Hop Pellets - 1 oz (28 g)
Star San Sanitizer - 16 fl oz (473 ml)
Citra Hop Pellets - 1 oz (28 g)