A door metaphor

If your key doesn’t work, make sure you’re using the right key.

Then, see if its teeth are worn or the blade is bent.

Check the lock, too. It might need to be lubricated.

Or the mechanism could be broken.

Someone might have even changed the lock.

The point is, there are a lot of reasons a door might not open for you. Even the possibility that you’re at the wrong door.