Changing icon results in generic PNG icon
I'm trying to change the icon on a folder on my MacBook Pro. I copy (Edit>Copy) the image I want to replace the folder icon with, select "Get Info" on the folder, select the icon at the top left of the window and then click "Edit>Paste."
Instead of changing to the picture I want, however, the folder icon changes to a generic PNG or JPG icon. I have restarted my computer, tried different folders and pictures, but nothing seems to help.
How can I fix this?
MacBook Pro 15″, macOS 11.5