You cannot create an account without a date of birth. The date of birth is what decides whether the account belongs to a child.
On the User Portal sign-up page, and as the first step when creating an account in the mobile app, you will be stopped. The message names the field: "Date of birth is required" (a full stop at the end is fine). You will not see a vague "Invalid request data", and an account will not be created without a date of birth.
On the phone, that step cannot be skipped.
If you entered a date of birth by mistake — especially if a portal or sign-up now treats you as under age and will not let you continue — contact support and say you entered the wrong date of birth.
That is a recognised request type. Support reviews it. If the correction is appropriate, they update the account so you can proceed.
Do not create a second account to work around it. Wait for support to finish the review.