This is a common problem whereby users would change the resolution of the NVR so that it no longer displays on any screens they have.
The objective is to reset the NVR’s default settings.
Open up SADP program (download here – https://www.hikvision.com/en/support/tools/destop-tools/sadp-for-windows/ SADP will give you the IP address of the recorder . You should see the IP address next to the NVR model number.
Open up an Internet browser and type in the IP address of the NVR.
Log in using username and password of the recorder.
SYSTEM > MAINTENANCE > DEFAULT – Restore all parameters to Default settings.