Since iOS 14, apps on Apple devices need to be granted permission to use the local network.

The first time you run iViewer on iOS14, it will show a popup requesting permission with a message like “iViewer would like to find and connect to device on your local network”.
You must allow this permission for iViewer to work on iOS14. Otherwise iViewer will not be able to communicate with any devices on your local network.

If the user accidentally taps “Do not Allow” on this popup, then local access will need to be manually enabled for iViewer under:
Settings > Privacy > Local Network