TikTok keeps marking my audio as "Unavailable" unless I use the original sound

I'm having a weird issue on TikTok and I'm wondering if anyone else has experienced this.

I make anime edits. When I download a sound I like and edit it into my video instead of using TikTok's original sound, the video gets almost no views, and the audio shows as "Unavailable."

If I use the same sound directly through TikTok's built-in sound option, the video performs normally. The problem is that using TikTok's original sound mutes or overpowers the anime dialogue and sound effects in my edits.

I tried lowering the volume of the original TikTok sound while uploading so the anime audio could still be heard, but then the sound often ends up showing as "Unavailable" anyway.

I'm just trying to understand why this happens and whether there's a way to avoid it while keeping both the TikTok sound and the anime audio.