OK I have now gone through and applied each of the 10 firmware updated one by one and tested all ok after each.
There was a bit of a hiccup after applying V4.60.000 build211129; the NVR rebooted OK but only 1 camera came up, the other three all said Incorrect Username or Password. Whilst I was having a think, after a couple of minutes, a second camera came up, but not the other two. Then as I was manually entering the user name and password for camera 3, both Camera 3 and 4 came up. So I though I would perform a Cold Boot, rather than a Reboot to see if it was a junk in memory issue like you sometimes get with PCs. Executed a Shut Down and then Powered off, waited a minute, and then powered on again. This time 2 cameras came up, the other two complaining of Incorrect Username or Password. Went to have a cuppa to see if the other two would come up after a while, but when I returned, they had not. So I manually entered the Username and Password for each of those cameras, and they came up.
Wondered if there was a bug in this firmware, should I roll back to V4.51.025 build210927 which had worked fine, or update to the next Firmware V4.61.000_220507 and see what happens, which I did.
V4.61.000_220507 worked fine, so I then completed the final update to V4.61.025 build220905, which went fine and all is working as it should.
I have to say that this is the first time I have asked for help via this forum since I bought the kit in 2021, and the response has been AMAZING, way beyond my expectations! It was fast, with detailed practical advice and the steps to take to get the NVR updated to the latest Firmware. so @Dan, thank you very much.
I can confirm that the Virtual Host enabling direct connection the the cameras is now working. No video working in the Browser connection of course, that has not worked for years, but the Configuration Tab and sub menus work great. So I can confirm that the Camera details are:
Camera 1 DS-2CD2355FWD-I
Firmware V5.5.3 build 171025
Encoding Version V7.3 build 170929
Web Version V4.0.1 build 170711
Plugin Version V3.0.6.26
Camera 2 DS-2CD2T55FWD-I5
Firmware V5.5.3 build 171025
Encoding Version V7.3 build 170929
Web Version V4.0.1 build 170711
Plugin Version V3.0.6.26
Camera 3 DS-2CD2T55FWD-I5
Firmware V5.5.3 build 171025
Encoding Version V7.3 build 170929
Web Version V4.0.1 build 170711
Plugin Version V3.0.6.26
Camera 4 DS-2CD2T55FWD-I5
Firmware V5.5.3 build 171025
Encoding Version V7.3 build 170929
Web Version V4.0.1 build 170711
Plugin Version V3.0.6.26
Many thanks for your outstanding help and support
@Dan.
Edmund