What might be the reason you cannot see anything through the MDO when sighting in downrange?

When you are trying to sight in downrange with a Miniature Reflex Sight (MDO) and nothing is visible, one of the primary troubleshooting steps is to ensure that all protective covers are removed. If the eyepiece flip-up lens cover and the objective flip-up cover are still in place, they will block any light from entering, making it impossible to see the reticle or the target. Therefore, flipping these covers open is essential for proper visibility.

While other factors like focus adjustment, battery status, and lens cleanliness can impact sighting effectiveness, the immediate action to take when experiencing visibility issues is to clear any obstructions, such as lens covers. Hence, ensuring that the covers are flipped up is a direct solution to the problem at hand.