I'd just like to add my recent experience. Had a customer's 7608NI-E1 NVR ready to upgrade firmware. (I noticed quite a few of those models were mentioned in this thread. It's the first HIKv NVR I've ever had do this during a firmware upgrade.
I was connected to it from my laptop via wifi. (not sure but that may have been the problem) anyway, ran the firmware upgrade, appeared to be going smooth and then nothing. NVR totally bricked, no video from HDMI/VGA, no presence on SADP, etc. I took it back to the shop and began studying this thread, and experimenting the hikvision
tftp (which by the way is hard to find anymore. I found it on an archive.org site via a google search). Like others it took about 5-6 tries and a few mistakes. I'll try to list frtom best of my memory what was going on that finally worked.
Used a switch between NVR and PC
used the 192.168.0.128 and tftp program
I did NOT rename the digicap file to digcap like the readme instructions suggested. (I did at first and then renamed it back to digicap and it worked).
turned all windows firewalls off on PC
ran and ping to NVR 192.168.0.64 -t and was finally able to get a reply (like only 2)
then a few trial and error starts of the tftp program and the NVR.
What finally worked was double clicking the program and powering up the NVR at exactly the same time. Once it connnects it's immediate, like in the first 5 seconds. I had no luck on previous attempts waiting the 5-6 minutes like some others.
The transfer process was pretty quick (like under a minute) and then another 4 or so minutes to apply it. I looked up and saw 8 beautiful "No Video" squares on the monitor.
Just had to go back in and reset all of the customers setting/IP's,
DDNS, etc and all worked like a champ. Even the previously stored video was still there.