i have a SPRING Ksg Thompson M1928 (military) handguard with a stick and drum mag

it has been used a few times for local games, but it still shoots as it had been when i first bought it

all stock parts,

going for $50
bought it for 100

my air nozzle broke so i had to take it apart to replace it, after buying one from APD, i put it back together and now it no longer fires, the motor is running,the battery is in shape, the only thing i can come up with is somethign is wrong with the anti reversal latch.

anyone have suggestions to what else can be wrong with it?