Why can't I go live on TikTok? There's no LIVE button on my account.

It's almost always the follower threshold. TikTok requires 1,000 followers to unlock LIVE, and you need to be 18 or older to host one. Under 1,000 followers and the button simply won't appear. Once you hit it, LIVE shows up in the '+' create menu next to Post. A few other things can hide it: a brand-new account, a recent community-guidelines strike, or region restrictions. If you're over 1,000 followers and 18+ and still don't see it, update the app and check TikTok hasn't flagged the account.

1,000 followers and 18+ is the requirement, that's why the button's missing for most people. There's no hidden setting to force it, you just have to reach the follower count first.