If your iPhone is unable to detect a specific 5GHz Wi-Fi network, the issue may be related to your router’s security settings. Many routers have a feature called MAC address filtering, which can either allow (whitelist) or block (blacklist) devices based on their unique MAC addresses.
It’s possible that your iPhone’s MAC address has not been added to the router’s whitelist, preventing it from connecting to the 5GHz network. Alternatively, your iPhone’s MAC address might have been mistakenly added to the router’s blacklist, blocking access to that specific network.
To resolve this, you should contact the service provider or the agent who installed your router. They can help you check the router’s settings and confirm whether your iPhone’s MAC address is listed correctly. You may need to provide them with your iPhone’s current MAC address, which you can find by going to Settings > Wi-Fi, tapping the “i” icon next to your connected network, and looking for the “Wi-Fi Address.”
If you have Private Wi-Fi Address enabled, inform the agency not to incorporate the device MAC address. Instead, they should use the Private Wi-Fi MAC address for filtering.
This issue appears to be related to the router’s configuration rather than a problem with your iPhone itself.