If the vocal track is indented under another track, that means it’s “inside” a folder track (the first track tat isn’t indented, above the indented track). If you have the vocal track unmuted but the folder track is muted, make sure to unmute the folder track as well.
If that’s not the case, you may get a clearer answer if you’re willing to provide your REAPER project file somewhere for download.
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!