Bought myself a blasting cabinet from harbor freight and am having trouble getting it to work... I've never owned a sand blaster before, so I didn't really know what to expect. Seems as if too little material is coming thru the tube- switched to a larger nozzle, but that didn't help. Running it at 100psi, medium grit 1/4" nozzle.

It takes a lot of air to run a 1/4" nozzle. Is your compressor large enough to keep up?

Moisture in the compressed air or ambient air can also clog things up.

try dropping it to 90psi. Is the media nice and dry?