First make sure that your shotgun can cycle 2 3/4 inch shells. To do this, read the barrel, if it say 2 9/16 shells then that is your problem. Early 16ga. Browning's were made to cycle 2 9/16 inch shells. Next, check your ring setup inside of your stock, it may not be set properly.
You need the services of a gunsmith. There are about a half dozen or so reasons if not more.
Modern 16ga shells are 2 3/4". Older shells were usually 2 1/2" or maybe 2 9/16". You can buy 2 1/2" 16ga shells from Polywad and also RST I believe.
12 gauge
I have a Winchester 16ga model 1400 I got it a few days ago I cleaned it and went out to shoot it but it does not want to eject the empty shell, what could be the problem, anybody?
Yes
Give it a thorough cleaning.
Ammo, parts, dirty
What I did was unplug the power cord from the back and then hit the eject again when it was plugged in again and it worked.
The weapon may not be a semi or an automatic one.
You need to have a gunsmith look at it.
You need to see a gunsmith.
This shotgun needs to be examined by a gunsmith.