It's a common issue for users with the dual band router models. These routers don't always allow the devices connected with their 2.4 Ghz wireless band to communicate with the devices connected to their 5 Ghz wireless band. It's especially confusing that the two wireless bands share the same wireless network name so you can't easily tell which band your mobile device and WiiM Mini are connected to respectively.
You can fix this issue with the following steps:
1. Give the separate network names to your 2.4 Ghz band and 5 Ghz band WiFi
2. Connect your WiiM Mini to your 5 Ghz band if possible
3. Connect your mobile device to 5 Ghz band when using WiiM Mini
If your router doesn't allow to assign different network name to 2.4 Ghz band and 5 Ghz band (which is rare), please set your WiiM Mini to connect via 5 Ghz band only by selecting device tab > device setting gear icon > WiFi status > 5 Ghz band only.
If you still have problem to find your device on the WiiM Home App, please send us a feedback and we'll look at your issue immediately.