I fired up the onvif DM and it wouldnt find the cameras - is this because they're connected through the NVR?
By default, the NVR PoE interfaces network is not accessible from the LAN network, so ODM won't see them from the LAN. And it won't see them if their IP address is in a dfferent range than that of the PC. So -
Do you know if the cameras were configured with a static IP address, and do you know what they were?
On the NVR web GUI, check out and note down the IP addresses that each of the PoE ports are using.
By default it will be something like 192.168.254.2 and upwards.
Set the mode of the ports to 'Manual' instead of Plug&Play. ('Modify' button)
If the cameras had static addresses - on a temporary basis, - hook up your PC to a spare PoE port, set the PC IP address to something in the range the cameras were using and you should be able to browse to the cameras known IP addresses.
Then set each camera IP address to match that of the PoE port it's plugged in to, from your check above. Something like 192.168.254.2 and up.
Then change the PC IP address to, say, 192.168.254.100
At this point, ODM should be able to see the cameras, if they are ONVIF compatible.
With the PC back on the LAN, and it's IP address back to normal, on the NVR web GUI in Camera Management, pick a port with a camera, change the Protocol to ONVIF, change the port number to the ONVIF port that ODM showed, and if you are lucky the camera will connect. Given correct logon credentials.
Quite a few 'ifs' there - but easy enough to try.
Good luck!