Why are popular songs missing from my Instagram business account?

That’s usually a licensing restriction, not a bug. Instagram’s licensed music library is mainly for personal, non-commercial use, so some business accounts and some post types don’t get the same popular-song catalog. Availability can also vary by country or region. There isn’t a setting that reliably unlocks every track for a business account. For commercial content, use Meta’s Sound Collection or music you’ve licensed yourself. If a particular song matters, check whether it’s available on a personal/creator account in your region before building a post around it, but don’t use copyrighted music commercially unless you have the needed rights.