Is the gun a springer or a PCP?

If it's a springer and you've zeroed it from a prone/bench position, you'll find that the recoil will shift your POI when shooting from standing.

When zeroing a springer it's best to set your sights from the position you'll do most of your shooting from

To test it out, use an oversized paper target at your given range - fire 5-10 shots from a bench/prone, then at a similar target from standing. If your groups still decent, but off from where you're aiming then it's the kick of the gun shifting your POI

HTH,

Dan