This is narrower than an update to all game sound. It does not say that sound effects, phone notification volume or audio from other apps were changed.
How to Check the Fix
Open the updated v1.2 app and go to a screen where its background music is playing. Move the in-app music control from a higher setting to a lower one and listen for a change. Test it in more than one part of the app if the first screen has no music.
If the control still appears unresponsive, check the installed APK version. Also note whether no sound plays at all or whether sound plays but the slider cannot change its level. Those are different symptoms. Your phone’s media volume can affect what you hear even when the app control is working.
Which Android Users Does This Affect?
The fix is listed for Android v1.2. Mega888’s version catalogue also names other builds, so the date alone does not establish that every Android installation received the same change. Compare the version on your phone with the version offered through your usual access route before replacing an app that works.
If the music control remains unresponsive on v1.2, record the phone model, installed version and screen where it happens. Those details make it easier to distinguish this issue from a game-specific audio problem.