Because the probiotics are freeze dried, they are in an inactive state and stable at room temperature for up to two weeks. The probiotics are only activated once exposed to moisture.
If your probiotic was left out overnight at room temperature with the cap tightly on, your probiotic is completely fine!
If your probiotic was left out overnight with the cap off, you should check the powder inside. Especially if it is excessively hot or humid in your area, you should check for your powder's viability by examining the powder for any unusual scent and/or any clumps in the powder. If your powder is still light and fluffy, it should be fine. Any powder that has started clumping has probably been activated by moisture and is no longer viable, and should be thrown out.
This article applies to: GutPro™ Powder, GutPro™ Infant, Primal Gut™ Powder