Strange thing is I have only started to get this error since recording to a NVR ....before I used to record to NAS and I never used to this on my iOS devices?
Are you trying to playback the downloaded files using a default media player on your iOS device?
As the error says it is likely you are recording the camera to the NVR using Hikvision's latest H.265+ compression and this compression level is unique to Hikvision so a lot of 3rd-party video players will not be able to unpack the CODEC. Your best option to view downloaded recordings on an iOS device is to set the camera to record with H.265 instead of H.265+ and then you should be able to playback those downloaded files. (you may have to download a more universal video player like VLC)
Yes, the IMVS app. When you have clipped a recording it saves it under ‘Pictures and Video’ ....and from there you have the option of ‘sharing’ the clip
We would recommend that you use the Hik-connect app instead of iVMS-4500, also I would log in to the NVR using Internet Explorer and check the video settings for that camera to see what CODEC you are using.
What camera model do you have? Are your camera and NVR running the latest firmware?