This usually happens because FCC hasn’t received acknowledgement of course completion from the CodeRoad course. If you go back into the project and ensure that you have clicked ‘Continue’ on the course completion message there and then go back to the URL submission page and try again, it should work?
If that doesn’t work, there are a couple of other things which you can try from this post (which is linked in the main Relational Database course page): Running the Relational Database Curriculum in your Browser