Step 1 Right click mouse and click main menu
Step 2 select Info.
Step 3 Clieck Version.
There is another way to check SN of system.
Step 1. Turn on DVR and connect DVR to a monitor. Right click mouse and select guide.
Step 2. Click next
Step 3. Scan QR Code to download APP or read S/N
If you have not connected DVR to a monitor and can not log in system, there is another way to find your system's SN.
1. Plug DVR to router by ethenet cable.
2. Get a computer which is connected to same router as DVR is connected.
3. Install a software on computer. Here is sofrware. https://www.dropbox.com/s/1ojt04nokwx1njg/upgrading%20software.exe?dl=0
4. Check if the software can detect system's serial number.