Hello wwxcharlotte!
I've had success downloading the Graph Data Science Playgound from the "File or URL" install box at the bottom of the "Graph Apps" tab. I recommend deleting the app that is giving the error, if it is in the list, and then copy and paste "MyJFrog - JFrog Customer Portal" into the "File or URL" box and hit Install.
If that is successful, I then recommend going to your Project and starting the database, and then selecting "Open" with "Graph Data Science Playground" and a pop up will appear to walk you through connecting them.
Let me know if this helps at all and where you get stuck!