Free spins for registration are available only if you registered via an affiliate link.
If you registered via a valid affiliate link or website, please complete your registration by filling in your full name and date of birth to your account.
Doing this should send you a Notification, which can be found via the Bell icon near your balance, or this bonus will be visible on the bonus page.
Unfortunately, this bonus is unavailable for your account if it's not there.
There are many factors in which the bonus won't apply:
Country restrictions.
Duplicate levels.
Incorrect registration.
Incorrect affiliate link.