Just bought and turntable won't turn
If it's under warranty, take it back.
I think the turntable on this model is driven by a synchronous gearmotor in the bottom of the oven, but it may be driven by a belt connecting it to a motor somewhere in the back behind the big transformer on the right side. (If the motor is under the oven cavity, there is probably an access panel on the bottom of the oven.)
If you know how to work safely around high voltage circuitry, you can check for voltage at the motor terminals to verify that there is no electrical fault. Sometimes the lubrication in the gearbox fails and the motor stalls. I've heard you can occasionally gets these to work by putting the gearmotor in the sunny-side window of a car to get it really warm, then squirting a few drops of light oil on the gearshaft next to the motor casing and putting it in a cool environment. If all goes well, the contraction of the air in the gear box sucks the oil in and it thins out the lubricant.