To use LIVE on TikTok, you must:
• Be at least 18 years old to go LIVE (this requires a government ID).
• Be at least 18 years old (or 19 in South Korea) to send or receive Gifts during a LIVE.
• Have 1,000 followers to go LIVE (may vary across regions).
But also if you have a UK/AUS account (where it was created not necessarily where it is now) you must verify your ID & Age.
Also if you bought the account (which is against the T&C's) you can be banned from live and even the account and any other accounts you have if caught, the account could also be a UK account if that's the case.
And finally here's the one that gets most people, if your account is a gaming account or uses gameplay in the videos your live requirement is a bit different and you require 10,000 followers rather than 1,000.
https://support.tiktok.com/en/safety-hc/account-and-user-safety/age-requirements-for-tiktok-live