So if D4 is on that same external switch, and it’s working and correctly assigned a 192x address from the router, D2 and D3 should look the same.
Fastest way out of the mess is to 1) delete D2,D3 from the Reg page, 2) default D2/D3 by either their GUI or the onboard factory default button, while connected. They should be assigned a 192 address.
Then connect the switch back to the NVR, discover them, and manually add to the bottom pane.