If you describe your scope a little better, some of the experts may be able to provide a more intelligent answer.
Fixed or variable? Adjustable Objective? Side Focus? First Focal plane or Second Focal plane reticule? (Brand and Model may help as there may be someone out there with the identical scope who has the answer you seek.)
Most scopes have a minimum range. For example: Good scopes designed for air rifles will focus at 10 meters because competitions are often at that distance. Scopes designed for long range shooting will often not focus on targets that close.
With my second focal plane scopes, I bring the reticule into focus by screwing in or out the rearmost lens until the crosshairs/reticule are in sharp focus. They tend to stay in focus even as I change power or adjust my focus. I don't own any First Focal Plane variable power scopes so I can't speak to those.
All the best,
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