Don W and Greg are on point, if nothing has been damaged by handling, (most likely would be the nozzle,) then likely you have a Vallejo/alcohol mess internally. X-20A smells just like alcohol, the label states butyl alcohol is one of the ingredients.
I once forgot the incompatibility problem with Vallejo and alcohol, I learned a lot about cleaning an airbrush in that episode. It turns thick and gummy, only a proper cleaner and implements like brushes will be sufficient for removal.
First, avoid soaking the airbrush body in any cleaner with the air valve in place. Second, a complete dis-assembly of the components will give access to the body chambers that are clogged.
Soaking the individual front bits, (nozzle and aircap,) in lacquer thinner will start to break down the mess, making removal easier. Since the needle was buggered far back, I imagine the bearing might also be.
Removal of the needle bearing is easy, just a tiny flat blade screwdriver will do it. Soak that as well, cleaning it with cloth and brush. Re-assemble and adjust the bearing nut for desired drag, just a bit is needed. Follow Don's advice on his site, use a toothpick to get the threads started, then the screwdriver to tighten. Very tiny part.
Using a small LED penlight will show you where the body internals are clogged, the interdental brush, sharpened toothpicks and cloth bits will do well for you.
Don's trick to use paper towel rolled into a fine point will go far in reaching into the tiny bits like the nozzle. Please have a good look at "Don's airbrush tips," all you need to know will be found there. Plus, either consult your manual or look it up on line, the parts placements will be seen there.
Hope you get it sorted soon, best luck.
Patrick