Blocked nozzle tip
Don’t throw away a can of spray paint when the nozzle is not working. If there is still paint inside you can easily swap the nozzle with another one from another can of paint that is working. Just pull it off and swap. Clean it when you are done by turning the can upside down and spraying till it is clear. Then you can return the nozzle to the original can if you want. To get really geeky, order extra nozzles online. — KK