You cannot request update to the capabilities using PUT for URI "/ISAPI/Security/adminAccesses/capabilities"
Try this and you should be able to enable the RTSP
You can get the <ID> of RTSP in "/ISAPI/Security/adminAccesses/capabilities" URI.
For DVR-H2T80B-41-HIK with firmware, DVR4-H2T80B-20181208 had to open the RTSP port
Check the capabilities -
http://<IP_ADDRESS>/ISAPI/Security/adminAccesses/capabilities
You can see which ports are open on the DVR
If RTSP is available then enable using the PUT method
Then you can access the...