Hopefully you were updating because the firmware was fixing a problem you had.
A common theme around here is don't fix what ain't broke. If the unit is working and meets your needs, in many instances an update breaks what you had working and provides you with something you didn't need. A Dahua Z12E that someone updated and then constantly reboots comes to mind, and a certain Dahua PTZ that loses autotracking with an update come to mind, a Hikvision ANPR camera losing half the FPS and loses the ability to read US plates - those are big deals to have happen. Don't do it unless it is fixing a problem you are experiencing or adds a feature you really need.
If you do decide to update, it is best to obtain any firmware updates from the vendor you purchased it from so that you do not run into issues. Any firmware you find here or elsewhere is obviously proceed at your own risk. We have many threads here where someone tried an update with a firmware they found on the internet and bricked their unit.
Many units being sold are Chinese hacked units that will either brick or go into Chinese upon updating. Some vendors will be upfront and tell consumers that as part of their website, but many do not or the consumer forgets...here is one such example....
Hopefully it is something simple like the resolution changed and you just need to get into the NVR via a webbrowser and downrez the resolution.
You may have to factory reset everything and start over.
@alastairstevenson is our resident Hik NVR figure outer, so hopefully some ideas or suggestions will appear.
