Hello!
I managed to find the answer to the question I asked the other day on my own. All I had to do was add the following settings to the “proguard-user.txt” file:
`
-keep class com.unity3d.player.UnityPlayer { *; }
-keep class inappbrowser.kokosoft.com.Helper { *; }
-keep class inappbrowser.kokosoft.com.DisplayOptions { *; }
`
Sorry for the trouble.