The guarantee runs 60 days from purchase, and the FAQ asks you to use the product consistently for at least 30 days first.
There is a 30-day use expectation and a 60-day window. Use it consistently for the first, then contact support inside the second if you are not satisfied.
Save your order confirmation, note your purchase date, and set a reminder before day 60. Read the refund policy page for the exact process, since this guide only reflects the FAQ wording.