If your motor doesn’t start or the blades are simply not rotating even though the motor works, there are a couple of things you should check before getting in touch with customer service:
Make sure the jar is properly and securely placed on the motor base. Most Ninja models need to be twisted until you hear a click and feel the jar lock in place.
Check if the lid is securely placed and closed.
The blender jar shouldn’t be overfilled. Find the “Fill up to here” line on the jar or simply leave an inch or two of space in the blending jar.
Make sure that the plug is securely inserted into the power source and that the power cord looks fine without any exposed wires.
If the motor base of your blender is hot, it might have overheated. Unplug it and wait about 15 minutes for it to cool down. If the problem persists, get in touch with customer service.