No sound when exited out of app and re-opening the app (iOS)

This bug happens when I exited out of Minecraft and re-open the app. Before I exited the app, there is sound, but when I closed the app and then re-open it, the sound is gone. I made sure that the volume in the app is loud enough, but it still doesn’t solve the problem. There is no problem with the volume of my phone. Below is the attachment that shows the bug in action.