You have 60 days to decide, and the brand suggests 90 to 180 to judge. A plan lets you use the time well.
Before the first gummy, rate energy, mood, sleep and training from 1 to 5 for a week. Keep other habits steady. Rate the same things at week three, day 30 and day 50.
At day 50, review the notes and decide whether you would continue. That leaves ten days to request a refund if you decide not to.
If you continue, do it knowingly, since the refund option has ended. Re-rate at day 90 and, if you go on, at day 180. If your ratings have not moved, you have a clear answer, and if they have, you still cannot be sure of the cause. Keep it simple and honest.