Door lock not unlocking with key fob or key

Hello, thanks for using 2CarPros.com. It sounds like the key cylinder, where you actually insert the key may be bad. Does the key work okay for all the other doors? The cylinder is replaced from the inside of the door panel. They are relatively easy to take apart. Here is an article on removing the panel from the door. You can see everything pretty easy once the panel is removed. https://www.2carpros.com/articles/door-panel-removal