Same here, I tried changing language to Japanese in game and on battle.net. It downloaded and applied an update but the language did not change in game.
Hey, Kama! Moved you over to a new thread, since the other one was inactive for some time. Japanese only supports subtitles at this time, no audio is available for Japanese. Are you experiencing any issues with the subtitles appearing?
Note: The following languages only support subtitles and audio is not available for these languages: Chinese (Traditional), Chinese (Simplified), Japanese, Korean, Polish, Portuguese (Brazilian), Russian, Spanish (Latin American)