With any new rifle of any kind, you have to zero it off a solid bench. I mean solid, not wobbly picnic table, but something that will not move. Take the shooter out of the equation as much as possible. Bench shooting also helps overcome flinch. When I went back to flinters after decades of centerfire, I shot off the bench exclusively until I could follow through and get good groups.
Once you're shooting good groups off the bench, get off of it and test the shooter.
If it won't group off a rock solid rest, it could be load, rifle, or shooter. Eliminate one thing at a time until it works.