First, know why it happened, because it changes the fix. Most link-in-bio pages sit on a shared domain (linktr.ee, beacons.ai, allmylinks.com) used by millions of accounts, including spammers. When enough of them get reported, Instagram filters the whole domain, and your page gets caught even if it's spotless. It's usually not you. It's the address you're on.
The quick fix you'll see everywhere: remove the link, wait a day, re-add it. That buys you a little time. But you're putting the same link back on the same flagged domain, so it tends to come right back.
The fix that actually holds: move your links to a domain that carries its own clean reputation instead of a shared one. A link on a domain that's been online and trusted since 2005 doesn't get swept into the shared-domain filters that catch the newer tools. That's the whole reason itsmylinks exists, and it's free.
One more thing while you're in there: your link has to go in the Website field of your profile, not the bio text. Instagram only makes that field clickable. A URL pasted into your bio just sits as grey text.