Why can’t I switch on the 18+ mode?

The switch appears only when the birthday on the account says 18 or older. A guest account cannot use it, and neither can an account that Google Play says belongs to someone under 18, or one whose age a parent set. If you have just added or changed your birthday, a change that makes you older takes 3 hours to take effect. The 18+ mode is in the Dochi AI app, not on the website.