Are you playing the Android version realMyst or Riven on a mobile device?
Noodlecake Studios developed the realMyst and Riven games for Android OS.
For help with any issues you may find in the Android version of the games, please reach out to Noodlecake Studios directly at this page: https://noodlecake.com/contact/
https://noodlecake.com/games/realmyst/