If you are absolutely sure the round is empty. It is just an empty casing in the pistol.
I would look at a few things.

First, Have you removed the magazine from the pistol.

Is the round jammed in the barrel? and is it and external ejector, and if so is it hung up on the rim of the case. Can you use something to get in and move it of the case rim. and move the slide back.

Can you put a dowel rod in the barrel and tap the casing back to see if that will free it up.
Use caution and remember that the firing pin is behind the casing. So as not to damage it.

I had a jam once and could not do anything until the mag was removed, once removed things went very quickly in getting the case out and things back to normal.

If it comes to it. You may have to send it back to FN for repairs.

Good luck.