A firmware update was recently released for the NVR6XX-4KS2 series devices.
Information, instructions, and download links can be found Here
From Dahua Wiki
I can use “Ping” to test that the IPC is on line after upgrade, but fail to log in.
Possible reason: Check if the WEB port was modified.
- Reset the device and log in again.
- Re-upgrade through 3800 port of config tool (3800 needs to upgrade matched program).