If you are being demanded to provide age verification, then this is usually due to either a Date of Birth being added that makes you below the age that an account be legally held. They will also offer the option to have the account supervised, if indeed it belongs to a child.

You can verify your age on your Google Account with these steps: Sign in to your Google Account privacy page. Click Personal info. Click Birthday.

You may need to get a court order issued by a judge before the vital records office will change your date of birth. In most cases, the date on a legally-issued birth certificate is presumed to be correct.