For your Greystone RV17 oven, the issue with the knob not turning typically indicates the thermostat or oven control valve needs replacement. The thermostat is the component that the knob attaches to and regulates the oven temperature. We recommend checking the oven control valve or thermostat parts available for the Greystone RV17 model. You can view and purchase compatible replacement parts such as the oven control valve or thermostat control from our online store. Please review the parts carefully to ensure compatibility with your serial number. If you need further assistance identifying the correct part or verifying fitment, our customer care team is available to help you get your oven back in working order promptly.