Assume hardware is in working condition, and they are connected by wire in LAN. There are several points you may check if you cannot search IP cameras on recorder.
First, make sure:
1. Your IP camera is ONVIF standard, and video compression format is H.264.
2. Recorder is connected to the same router which is using with IP cameras.
3. (this point not for NVR) Default input mode of SDVR is for all analog camera, so right-click mouse -> Main Menu -> Switch -> ChannelType, switch to correct input mode then click OK to reboot.
Check IP Address
If above points are checked correctly, there may be IP address (subnet) problem. To make sure IP address is correct, please first check IP address of router:
if it is 192.168.0.1, then change SDVR IP address to 192.168.0.18 (right-click mouse -> Main Menu -> Network), and Gateway change to 192.168.0.1, do not change other setting, click Application and OK to reboot.
if it is 192.168.1.1, there may be IP conflict, please assign another IP address for recorder (or IP cameras).
Or you may set recorder to DHCP (Main Menu -> Network -> Networking), you need to turn on DHCP function on router as well.
If it does not work, reset network to factory setting (Main Menu -> System -> Restore -> Network -> OK).