The camera is working on the nvr
If the camera is connected to an NVR PoE port - SADP on a PC on the LAN will not be able to access the camera.
Did SADP show the camera - or just the NVR?
the password is not changing.
If the camera is on an NVR PoE port - how are you trying to log in to the camera and try the NVR password for it?
Have you used the 'Virtual Host' facility on the NVR - the links provided in the right hand column of the NVR web GUI 'System | Camera management' menu?
This can be enabled using the NVR web GUI Advanced settings tab in the Network menu.
If you end up having to use the tftp updater to reset the camera - you will ideally need to connect the camera to the LAN (maybe a router ethernet port) and power with an external 12v supply.
You could also try connecting the PC with the tftp updater to an unused NVR PoE port, and leave the camera connected to the NVR, but the tftp updater doesn't connect so well when the camera is powered over PoE.