The music completely turns off after I raise the volume from zero. I occasionally like to listen to music or videos in the background so I temporarily turn off the in-game music. After I'm done with said background music/video I go back into the options to listen to the game's OST but to no avail.
I also tested this out with the main menu music and it seems to be a problem there as well. I have to completely exit the game to get this working again. As of the moment I have to turn the game volume to 1.
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We're tracking this issue in MC-103511, so this ticket is being resolved and linked as a duplicate.
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I think that music turns on after some time, after couple of minutes etc. You just need to wait some time before music plays again. But I am not sure.