Copied application showing "prohibited" instead of app icon in Finder
I have seen Finder sometimes getting stuck still showing the last unfinished state of a file.  This may be a refresh issue, especially when you say that restarting the Finder solves it.

Alternatively, you could try to just run the application by simply double-clicking it.  If the "prohibited" sign is valid, you will receive an error message stating the cause.

Otherwise, it will simply work, potentially update the icon at that stage already or at least once you either restart the Finder or the computer.