A money-back guarantee is referenced across materials we reviewed for HorseFil, though the exact window has been described inconsistently across sources.
One independent review we examined specifically flagged that the guarantee window is described inconsistently across different pages of the brand's own website. A separate FAQ answer in that same coverage referenced a 60-day window with a specific return process (emailing support with “Refund Request” in the subject line and mailing back all bottles to a return address, with the customer covering return shipping).
Contact the official store directly with your order number for current return instructions, since the process and window have been described inconsistently across sources.