TikTok only allows 60 seconds of any sound recording to be included in a video if that sound recording has been distributed to them. As a result, if you or one of your artists uploads a video with more than 60 seconds of a track that you have delivered to TikTok, the track will be fully muted in that particular video.
There is no way to reverse this muting once it happens. The only way to resolve this situation is to remove the original video and reupload one with no more than 60 seconds of your track.