UV Map won't appear

Hello, I’m trying to UV Unwrap a rectangle box, and even though I marked the seams and applied scale, when I click “unwrap” nothing happens, the UV map doesn’t appear in the image viewer.
Any ideas?

Only selected geometry gets unwrapped.
So, make sure you actually have selected anything in Edit Mode before hitting U (or clicking unwrap).

If the Image Editor is currently showing ‘Render Result’, then delete it with the X button

Thank you for the responses! The ‘render result’ image was the problem.