Identify whether the task is local
Write down what the app is trying to find: a nearby receiver, a local media server or a remote internet source. A private local device and a provider’s internet address are different destinations. A Local Network permission is relevant to the former and should not become a ritual fix for every remote-stream error.
Check whether the target device is powered on and available through its normal interface. If it is absent from every device in the house, begin with that device or the network. If another app finds it but one Mac app does not, the app-specific route deserves attention.
Review the named app’s permission
Apple documents System Settings → Privacy & Security → Local Network, with an on/off control for each listed application. Inspect the actual player or helper making the request. Give access only when you understand why that application needs to communicate with nearby devices.
After a relevant permission change, reopen the app and repeat the same discovery task. Record whether the device appears. Do not reset all privacy permissions or disable the firewall simply because a targeted comparison has not yet been made.
Keep network separation in view
A permitted app can still fail if the Mac and receiver are on isolated networks. Compare the intended network arrangement, particularly guest Wi-Fi or a separate router. If the network is managed by someone else, ask about device-to-device communication rather than changing infrastructure you do not control.
A VPN may also change routing, but any change should follow the provider’s or organisation’s supported procedure. Preserve the original configuration. Broad network changes can interrupt other work while leaving a simple app permission problem unresolved.
Report the permission and outcome separately
For a useful report, include the macOS version, application version, target device and whether it appears in another supported app. State whether permission was allowed before the test and whether changing it altered the result. Keep device identifiers and private server addresses out of public screenshots.
If discovery succeeds but playback then fails, begin a second diagnosis at that later stage. The app has found the device; codec support, source access and output control are subsequent questions. A successful discovery check does not prove those other operations have completed.