Why unable to move gear shift from drive position to reverse?

If you're unable to move the gear shift from drive to reverse, it could be due to several reasons. Common causes include a faulty transmission range sensor, a malfunctioning shift interlock system, or low Transmission Fluid levels. Additionally, if the vehicle is not fully stopped, some cars have a safety feature that prevents shifting until the brake pedal is pressed. It's advisable to consult a mechanic for a thorough diagnosis.