It just probably needs to cook a bit longer; the cooking time depends on the size of your roast, especially its thickness. Overcooking can also lead to tough meat, so regard the cooking times indicated and only increase the time if your cut is obviously very thick.  The quality of the meat can also influence tenderness. Look for cuts with marbling and a moderate amount of fat, as this helps contribute to juiciness and tenderness. Incorrect pressure release: For a tender pot roast, it's recommended to use a natural release for a few minutes before using the quick release to release any remaining pressure.