Is the volume turned up on your tablet?
Does the sound work on non AI2 apps? or no sound at all using other apps too? The tablet might be set to mute or sound is turned of in the device Settings. Is this possible?
What kind of sound file are you attempting to play? How large is it (Mb)?
Do you have the sound file loaded in Resources (Media)?
Could you please post a png or jpg image of the blocks you are trying to use to play the sound. You said you tried different things,
if we could see some of your code, we might discover the issue.
Regards,
Steve