Does not lock - Daniel Defense Heavy Duty Push Button Quick Detach Sling Swivel

I recently purchased a Daniel Defense V7 rifle with the M-Lok attachment and then bought a Blue Force Gear padded vickers sling. All I needed was a push button QD sling swivel, so I purchased the heavy duty one from Daniel Defense. You would think that the DD sling swivel would fit into a DD rifle, but unfortunately that is not the case. The sling swivel fits on the rear of the rifle but not on the M-LoK part. The balls of the QD sling swivel do not go deep enough past the thickness of the M-Lok attachment and therefore doesn't lock into it. I am very disappointed. I don't have the time or the money to keep trying to find something that fits.