G34 Threaded barrel issue

Hey all... I bought a Faxon G34 Gen5 drop in threaded barrel. I put it in my G34 and had to give it a good push to seat right, but it seemed to fit well. However when I reassemble the slide onto the frame, it will go on, but I can't pull the slide back. In fact it'll only go far enough to let me release the tabs to take the slide back off. But that's it. Any ideas on what I need to do to make this work? I've never had a drop-in barrel not work after just dropping it in, so I'm at a loss 😂