PBS Kids' Apps - No Sound

On both my iPhone and iPad, the sound does not work for the PBS Kids Games OR the new PBS Play and Learn Science app. I have tried all troubleshooting tips provided by PBS, but none have worked. (All the tips are geared toward normal sound issues and adjusting the volume in various places on the devices. Sound on my other apps and elsewhere work fine). The app themselves do not have a volume option that I see. I have also tried uninstalling and reinstalling the apps, but that hasn't made a difference.

Has anyone else experienced and resolved this problem? Thanks!