Sounds like the clutch isn't releasing completely. Since the vehicle is so new, I'd look at a badly assembled pressure plate. If the pressure isn't equal at all points, one section of the pressure plate will not move as far away from the clutch disc, causing drag on the clutch and preventing you from getting the truck in first gear or or reverse. IF this is the problem, it should get worse as the clutch warms up with use.
Other causes, a misaligned transmission to bell housing. A piece of dirt or junk (a fallen washer when components were assembled at the factory) between the face of the transmission and bellhousing or the face of the bellhousing and the rear of the block. My Dad's new Ford station wagon had a tailshaft drip from day one. Dealer said it was 'normal'. Didn't drip much, maybe a half pint a year. Got tired of the drip, pulled the driveshaft, unbolted the tailshaft from the trans and found the parking pawl spring squashed between the housing face and the tailshaft face. A new gasket, some oilstone work to smooth the ding and the car never dripped a drop for the next 15 years.
Usually if this is the cause, the truck will be hard to shift thru all gears, synchro or not because of the drag.
If it's a hydraulic clutch, could be an air bubble in the line which compresses and lessens the throw of the release bearing. Anyhoo, it's under warranty, Toyota should fix the problme, WHICH IS NOT NORMAL.
Good luck.
I worked at a Chevy dealer the summer before I went in high school, washing cars. The truck came in loaded with new cars, among them a go fast 396 Chevelle with a 4 speed. The cars are unloaded in a certain area and we had to take them one at a time and detail clean them, remove shipping papers, etc. I start the Chevelle, push in the clutch, slide it in first and it sounded like a tin can with twenty quarters being shaken had next to your ear.
I get yelled at for breaking the car (I'm 15). The mechanic takes the car for a spin around the block and the clutch can't hold the torque. Floor it at 60 mph and the tach just climbs as you slow down.
Long story short, the factory put the clutch disc in backward, they put it in springs facing forward. Idiots. Mistakes happen.