Brand new? It will work itself out. Glock mags, especially when new, don't like to be fully loaded. I've had the same problem with my 26 and 21. Take your mags, fill them completely up, and let them sit for a day or two. Then try putting it in the gun. If that doesn't work, load 8, put one in the tube, remove the magazine, and put another round in there.
I've noticed with my 26's mag fully loaded it can be tough placing the mag in, so I have started giving it a little more force. As I stated though, that did eventually work its way out.