Yeah, this one's common. The suction control slider on the front of the cleaner head is almost certainly in the wrong position. It has three settings for a reason.
For deep- to medium-pile carpets and delicate rugs, the slider needs to be positioned all the way to the LEFT. If it's in the center (for low-pile) or right (for hard floors), the suction is too high and it'll suction-cup itself to the carpet.
Just slide that control to the left. You should feel an immediate difference. Also, make sure the brush bar is turned ON for carpets—that's the button on the left side of the handle.
IF THAT DIDN'T WORK: Check for a massive blockage in the cleaner head or hose. A clog will make it impossible to move. Unplug, remove the cleaner head, and check the brush bar and airway for wrapped fibers. Also, ensure the bin isn't overfilled past the MAX line.
HEADS UP: Some rug materials can fuzz if you use a rotating brush bar. If that happens, turn the brush bar OFF using the button on the handle and consult your flooring manufacturer's instructions.