DIAGNOSIS It feels stuck, but the shelves do come out—they're just a very tight, friction-fit design. People force them and break the plastic guides because they don't know the trick.
FIX Unplug and empty it. To remove a shelf, don't pull straight up. Push it UP from the very bottom center, using your palms. Once it's moving, tilt it forward (like you're dumping something off it) and then it will slide up and out of the side grooves. Clean with a mild soap solution, not harsh chemicals that can crack the plastic. Dry thoroughly.
IF THAT DIDN'T WORK If a shelf is truly wedged, you might have bent the interior wall guides. You'll need to gently flex the shelf itself while applying upward pressure. A second pair of hands to slightly push the interior walls outward can help.
HEADS UP Never use a steam cleaner or pour water directly inside. Water can run down into the lower compartment where the electronics and fan are and short something out. Always use a damp cloth, not a flood.