To reconnect an IP camera to an NVR security system after losing connection, first power on the camera and connect it to the NVR using an Ethernet cable. Then in the NVR system, go to the video management interface, delete the disconnected camera, refresh to find the new camera, and match the camera's code to complete reconnection. Once paired, the Ethernet cable can be disconnected.

1. When your ANNKE IP camera loses its connection to your NVR security
system, try this method in the video. It works for new cameras too.
First, power on your IP camera. Get an Ethernet Cable, plug one end of
the cable to the IP camera, and connect the other end to one of the LAN
Ports on NVR rear panel.

2. Then, enter the NVR system. Right click on the live monitoring interface
to enter the Shortcut Menu, choose “Video Manage” and log in. There
is no need of password by default, but if you’ve set a password before,
please input the password and log in.
Then you can see the Status of this camera is “IPC Disconnect”, choose
it, and click on Delete. And then click “Refresh”, there shows the IP
camera you just connected to the NVR via the Ethernet cable. Choose it
and click “Match Code”, wait a few second to complete.

4. Now, your IP camera is paired to the NVR again and you can disconnect
the Ethernet cable.
Watch more in this video:
https://www.youtube.com/watch?v=vfPmUhhEHWI