I have a NV751 that stopped picking up anything.

I open the rotating brush area and clunks of pet hair were bunched up everywhere.

Looking back UPWARD on the suction hose I discovered one of those bleeping Child Proof Outlet plug covers almost perfectly wedged in the hose and was perfectly BLOCKING the hose pickup.

It took a straight slot screwdriver and some needle nose pliers but I got it removed.

THAT WHAT THE ISSUE WAS !

The vacuum works like NEW again.

(I HATE those little outlet safety covers)

So if your NV751 is not suctioning, check filters first. From the rotator head, check back UPSTREAM and chances are that that is an obstruction somewhere in the hose line itself.

Good luck.