If you find the coffee is not brewing correctly, check first to see if steam is escaping from the area where the top and bottom are screwed together. Sometimes you’ll a little water bubbling out of here. If the connection here is not tight – if steam can escape out the side – the pot will not work. Try to screw the parts together more tightly next time. Hug the pot close to your chest and twist the top and bottom together as tightly as you can.
We had a similar problem with our old Bialetti machine bought in Italy. Turns out I’d been banging the coffee basket out of shape every time I threw the old, used coffee grounds in the compost bin.
The wonkiness meant that the steam generated could escape up past the coffee, so no pressure builds up and no water gets pushed up throught the coffee. Our solution was to put a rubber band around the coffee basket and that worked nicely.
You might also check that the filter-screen is clean – if this is clogged with coffee grounds or oils – it could prevent the steam/coffee from rising to the upper chamber.