(It should go without saying, but just to make sure it's extra clear) To play the game in the first place these days, you'll need the server replacement fix found here: https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2907945906

Here is the link hi click this text[mega.nz]

Just replace your existing "Game.exe" file with the newly downloaded one. It can be reached by right clicking the game in your Steam library, hovering over "Manage", and selecting "Browse Local Files". You can then launch your game through Steam as you normally would and should be able to play your M4A files alongside everything else.

Be aware that if you ever verify the game files, it could overwrite the exe with the latest one again.