What device is it?
You can try working through a whole lot of things including
- will the device connect to a different network?
- reset the device
- On the device, forget and reconnect to the hub
- check guest SSID is enabled - can you connect to that?
- security settings correct?
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I know a bit about Wi-Fi, Telecoms, and TV as I used to do it for a living but I'm not perfect so don't beat me up... If you make things you make mistakes!