This is likely to be the Hikvision 'Catch-22 trap' which appears to be aimed at bricking CN cameras that had 'hacked to EN' firmware where an update to 5.4.0 or higher is attempted.
A couple of forum members were generous enough to freely supply a couple of cameras to analyse.
What I've seen is:
The upgrade program when handling 5.4.0 or higher firmware first of all erases the flash areas holding the apps, then records that 5.4.0 was installed, then rejects the firmware that was downloaded.
This leaves the camera with no apps to run, it just boots into a bare kernel with no web services, not responding to SADP etc.
And because 5.4.0 or above has been loaded, any attempt to downgrade to a working version is rejected by the 'anti-rollback' block in the 'upgrade' program. And 'psh' is in play as the shell, so no commands of any real use are available. A bit of a deliberate trap.
Hence the 'Catch-22' comment.
I have been able to fix these cameras, but by a slightly convoluted process I wouldn't impose on a normal user.
However - I do believe I will be able to devise a fairly straightforward method of unbricking these problem cameras. I'm working on it just now, I need to do some testing.
Another interesting thing I discovered from the bricked cameras is that there appears to be a remnant of the original 'hacked to English' firmware method which the Hikvision code in firmware of 5.3.0 and higher is handling, such that another form of 'bricking' occurs based on an invalid device_type result.
So some cameras may also be bricking due to having a specific method of converting to English installed by the seller.
I know how to deal with this such that the 'bricked' cameras are OK running the 5.4.0 and 5.4.5 EN/ML firmware.
to help me in case of ...