What pressure are you spraying at?
Is the head of the airbrush on tight?
Is the siphon tube of the cup in tight?
Is the vent hole in the top of the jar lid open?
If that small vent hole in the cap is plugged the airbrush will not siphon as it becomes vapor locked.
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon