NotchMindReturn copies, it doesn’t paste
Pasting into another app means NotchMind presses ⌘ V for you, which macOS only allows with the Accessibility permission. Without it, ↩ copies the item and you paste with ⌘ V yourself.
Grant it in Settings → General → Permissions. If it’s already on but still not pasting, see a permission keeps asking.
It pasted into the wrong place
NotchMind pastes into the app that was in front when you opened clipboard history. If you clicked somewhere else in between, or that app was closed, it can’t paste there. Click into the text field you want first, then open clipboard history.
“Preview only”
Images copied from inside an app, such as a browser or a design tool, are kept as previews and can’t be pasted again. Images copied as files can. See use clipboard history.
The app doesn’t accept that kind of item
A file can’t be pasted into a plain text field, for example. Use ⌘ ↩ to copy it and paste where it fits.