I brought down the camera and conbected to the NVR with internet cable but the display screen still says "No Link".
Well, that presumably lets out the original ethernet cable as the source of the problem.
Finally, I connected the camera direvdir to the router with the power cable connected and this time, the Sadptool recognised it.
So it's not totally dead after all.
I can't locate the camera again in Sadptool tool.
This was still while connected to the router, with the 12v power supply?
Suggestions:
Presumably in SADP it showed an NVR PoE port IP address, something like 192.168.254.x
If it's coming and going in SADP - what does the link detect light on the router show? Steady on, with the traffic LED flashing?
If you can get it showing again in SADP - does the IP address match that of the channel in the NVR that it was connected to?
What firmware version shows for it in SADP?
If it's stable in SADP (use the Refresh button a few times) you should be able to change the 192.168.254.x IP address to one in the range that your LAN uses, knowing the password.
If you can do that - double-click the IP address shown in SADP and see what the browser access looks like.