We don't need to know the details, the OP can solve his own problem just by looking at the cassette and freehub.
In order for a cassette to be properly tightened on a freehub --- ANY cassette on ANY freehub -- it needs to overhang the front of the freehub body by 1-2mm so the lockring bears on the cassette and doesn't bottom out against the freehub face.
It's exactly comparable to how the steerer has to be below the top of the stack on a threadless headset system so th top cap can preload the headset.
So, to the OP, slip the cassette on, push it back and see if it still overhangs. If not add a spacer behind the cassette to bring it out in front.
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