Parental controls or restrictions, such as Screen Time, maybe block from allowing you to access games and the Grownups menu. Add and (our affiliated app) to your allowed content as well as http://localhost:3744 for Nogginville, then exit and re-launch the Noggin app. Launch a game and visit the Grownups menu to confirm this has resolved the issue. 

If you continue to have trouble with Noggin, please let us know.