Digital game and The CD

It's likely that the game disk has reinstalled information flagging the game as being installed from disk. You should be able to re-install the digital version from PSN again to 'fix' the problem. You may have to uninstall the game first but I have no direct knowledge of how your game may react.

Both the digital version and the CD version will work. Once you buy the digital version, the CD is no longer needed. Keep in mind that the digital version is attached to the account it was purchased for and it’s non-transferable. Meanwhile, anyone can borrow the CD and play that game wherever they are or on whichever account they are on. Virtually both contain the same game but physically the CD has more freedom of course.