The magazine should be able to be inserted without pushing the mag release button. You might want to send it in for a once over and for your trouble they will send you an additional mag as well to offset shipping costs.
What I have seen on mine is that I will put the magazine in and it will feel like its in, but it needs a extra push of about 1/4 inch to fully seat it.I may have just not been pushing in enough. I have tried it several more times and it seems to be in working order. If not I will simply send it in.