Are you using a short pellet?
Gecko or Hobby with the skirt seated around 1mm into the carriers will leave space in the front of the carriers for the mag advance mechanism, if the pellets are too far forward the Anics Skif will jam and fail to feed.
If it will cycle cleanly through an empty mag then the mag and gun are not faulty, if it won't cycle through an empty mag try a new one, the site owner JS Ramsbotom sell them at a very reasonable price, the mags don't last forever and while some will work if cleaned out with aerosol car wax (never grease or oil as these will collect dirt & performance will rapidly deteriorate) if that doesn't work they should be binned & replaced,
Regards,
Nick