Strange... Do you have any problems if you use the latest iVMS4200 software for PC? How many cameras do you have in the network? Do you get the same error for all the cams?
Here are some other tips:
- Make sure you use the latest firmware for the cameras in case you use English firmware (Chinese version is a different story).
- For iVMS4500: try clearing app data and cache.
- I'm still thinking of port 554 might be the problem. In case you have more than one camera in your network, you should change port 554 for all the cams, preferably starting above 1024, like IP1 - 1024, IP2 - 1025, etc.
- Also try disabling UPnP in the NAT network settings for all the cams, then reboot. Sometimes that could mess up the things.