Hi Alastair, thanks for your continued input.
I have reverted the camera back to v5.5.53 build 180730 and everything is back to working normally again,
except that Hik-Connect is now OFFLINE and will not connect. I can access the camera's remote configuration via IVMS4200, or a Chrome web session, or an MS Edge web session.
Interestingly, if you look at the screenshot I have included below, the NAT section of the Network Configuration settings, using this older firmware, shows everything is 'Valid', which was all showing 'Not Valid' using the latest firmware. Do you think this is significant?
I'm wondering if it's somehow linked to the custom port settings that you are using.
As a test - maybe revert them all to the original defaults.
With the latest firmware installed, as you suggested, I did try setting all the ports back to the default values and it made no difference. Adding the camera to IVMS4200 just resulted in a Timeout and the camera being added in Offline state despite Live View still being accessible from my NVR and Hik-Connect services, and of course web login and remote configuration still only possible with a legacy Internet Explorer client..
It is tempting to think there is something significant with the WebComponents add-in but then this would not explain why the camera does not Add properly into IVMS4200, or would it?. I read something somewhere about the introduction of Winsocket instead of WebComponents in the 5.5.82 firmware but I've no idea what that means.
So I am still in the same stuck situation with this camera.
The camera will not connect to Hik-Connect with firmware v5.5.53 b180730 but connects immediately with the latest firmware.
However, the latest firmware the camera times out (and shows status Offline) when adding to IVMS4200 client, and will only provide web access for remote configuration using a legacy Internet Explorer client which is due to me retired by Microsoft in May 2022.
Do you have any other ideas on what I can try?
Incidentally, I have 5 other cameras on exactly the same network and they are all working perfectly with their latest R0 firmware managed in exactly the same way as this camera. They are models DS-2CD2132-I and DS-2CD2332-I.