b. I can add a third party IPC but there is no display. What might be the problem?

Answer:

1. Check whether the third party IPC supports ONVIF.
2. Check whether the third party IPC has an ONVIF switch and if so, switch it on.
3. Check whether the ONVIF port is correct and correct if not.
4. Change the third-party IPC stream to H264 encoding format.