Avoid opening the cameras. Not even sure a reset switch is in there. In my experience, opening the cameras makes them susceptible to humidity and lens fog buildup down the line. In the remote device section of the nvr hit the modify pencil icon and that will bring up the settings for the camera. I think it's a good bet the password already set is admin. I wouldn't mess with the password. What I have found works is trying different ip addresses, staying within the switch ip address range of course. You'll notice all the cameras are in ip number sequence. Take note of the ip address for the camera you swapped out and maybe change the new camera to that address, if the nvr is addressing the new camera to a different address. It may be the nvr channel is looking for that original camera address. I've also had success readdressing cameras to one that fills in an address gap in the sequence with all the other cameras. The nvr auto switch addressing is quirky and I have found trying a different ip address, keeping the address in the switch range, ie 10.1.1.xxx, can get things going. Good luck.