Diagnosis
Your Denali Tanker pressure canner lid is stuck because there is still residual pressure inside the pot. The lid is mechanically locked by the pressure itself, which is a critical safety feature designed to prevent you from opening it while it's under pressure, which could cause a dangerous steam explosion and severe burns.
How to Fix It
Do not force or pry the lid. The correct procedure is to let the canner cool naturally and completely at room temperature. Do not cool it with water or move it to a cold surface. As it cools, the internal pressure will drop. You will know it's safe to open when the round, metal air vent/cover lock on the lid has fully dropped down. Only then should you turn the lid counter-clockwise to unlock and remove it. This can take an hour or more for a full canner.
If That Didn't Work
If the canner is completely cold and the lid remains stuck, ensure you are turning it correctly: push down slightly and turn counter-clockwise. If it's still stuck, a vacuum seal may have formed. Carefully and gently slide the tip of a thin, non-metallic utensil (like a plastic knife or a chopstick) under the edge of the rubber gasket to break the seal by letting a tiny bit of air in. Never use metal, as it can damage the gasket and lid sealing surface.
Heads Up
Forcing a pressure canner lid is extremely hazardous. Always verify the air vent/cover lock has dropped before attempting to open. Regularly inspect and replace the rubber sealing gasket if it becomes hard, cracked, or misshapen, as a worn gasket can contribute to sticking.