Slide does not retract?

Does the gun lock open when it is empty and the slide is pulled back on the empty mag. If it does not lock, there is a problem. Should lock when manually operated with an empty mag in it.

If so, do you have another mag to try the same thing in it again?

Possibe problems. The mag follower is not making contact with the slide release inside the gun. You may solve that with another mag. Or may be the slide release is damaged where it makes contact with the mag follwer.

Ya might want to remove the slide and work the magazine in and out of the gun to see if the magazine follower is making contact with the slide release where it should be. Should be visible right along the inside of the left frame rail, next to themagazine.

Ditto what Pancho says and if that all works, try a different ammo. What you're using might not be powerful enough to make the slide go back and engage the lock.

I had the same problem with a Thunder 380 I bought. After talking with one of the warranty centers I found out this was a common problem. The slide needed to be mated to the catch. Took about 5 minutes to fix it myself with a small precision file. Just go slow, it doesn't take much.

Remove your slide and look at the notch in the slide. Is there a small amount of peening? That was my problem. It works wll now.