Philips Hue Bridges will not complete setup or pairing

The checks in more detail

a network scanner app such as Fing or, on Windows, the Network item in File Explorer. Once found, follow the prompts to update the Bridge, which may need repeating, and the third light will come on when it is up to date. Then add lights by serial number or search, assign rooms and set up scenes. For the Bridge Pro, Hue has a separate setup article and, when upgrading from a V2, an in-app migration tool that transfers your settings, so use it instead of resetting.

If setup stalls, check the Ethernet link, restart the router, move the phone onto the same network as the Bridge and try again. A Bridge that was set up by someone else must be removed from their account first. Keep the phone's Bluetooth on during setup for some accessories. Keep the phone on the same network as the Bridge for the whole setup, since a phone on mobile data cannot find it. If setup works on another phone, the first phone's permissions or app version were the cause.

Set up when you are not rushed and have the router nearby. Add lights room by room, testing each before moving on, since finding a fault among fifty new lights is much harder than among five. The Bridge search is by network address, so a guest network or a VPN on the phone can make the Bridge invisible even though the lights are on, and turning the VPN off is worth trying first.