First off bro.
Your trans is prolly fine. So is the rest of your truck, most likly....

Pull it off and check the gears and shifting unit. This is a brand new truck that you just got. If you havnt heard it shift at all yet, its most likely just something simple.

Like stated above. You should check to make sure the set screw is still fully seated inside the unit (So its not binding.) Put it flush and do a 1/16th inward turn. get your engine running up to temp (since its still brand new) and then start driving. Make some LONG passes at about 3/4 throttle. So the rpm is SLOWLY accelerating, and then you should be able to hear the shift. Sometimes the truck shifts sooo quickly when you hammer it you cant tell that it already shifted into the next gear.
Report your findings back to us.