icoControl is depended on CoolMasterNet having a permanent internet connection to the iocControl server.
When this connection is lost, the control on the indoor units is lost via the app and an oval red icon with a red line crossing it will show on the app (as seen in the image below).
One of the reasons for this to happen is an a network communication issue, not related to CoolMasterNet.
To pinpoint the issue, look at the CoolMasterNet screen and locate the cloud icon on the bottom right corner of the screen (See article about the CoolMasterNet screen layout and error codes).
If the cloud icon is not to be seen, it might indicate on a network issue preventing from the CoolMasterNet to communicate with the iocControl server.
For cases like this, please try the following:
Check the the network cable is connected firmly on both the router/switch and to the CoolMasterNet
See that on both ends there is a flashing green & yellow light
Try to change network ports on your router/switch, to eliminate malfunctioning network port on the router/switch
Try to connect a computer with the CoolMasterNet network cable. See if you are able to surf the web using the same network cable. This is to eliminate bad network cable issues. If you do not have a different device to connect, try replacing the cable and test.
Try to restart your router
Try to reset the CoolMasterNet
If the cloud appear on the bottom right corner with a number inside of it, please refer to this article to see the cause with the communication issue.