If water does not flow out of the outgoing nostril (after giving it about 10 seconds to do so), before concluding there is a nasal blockage, check the following:
Relax in the nose and facial area.
Check that the end of the nose cone is not pushed against the inside of the nose thereby blocking water coming out of the pot. Align the spout in a straight line with the nostril passage, and don’t push it in too hard.
Check that the pot is tilted enough for the water to flow down towards the nose.
Check that you are not sniffing the water backwards towards the throat.
Check that the water is not leaking out of the ingoing nostril.
Check that the water is not too cold, since cold-water contracts the nasal passages.