Wi-Fi failures are split between phone-side (saved network gone stale) and router-side (band, channel, DHCP). The ladder below sorts it out fastest.
- 1Toggle airplane mode on/off, then Wi-Fi off/on.
- 2Restart both phone and router (router: 30 seconds unplugged).
- 3Forget the network (long-press → Forget) and reconnect, retyping the password.
- 4'Authentication error' with correct password = router-side; reboot it and check for MAC filtering.
- 5Connects but no internet? Try another network to isolate; check the router's ISP link.
- 6Reset network settings: Settings → System → Reset options → Reset Wi-Fi, mobile & Bluetooth.
Tip: Old phones don't see 5 GHz networks, ask the router to broadcast 2.4 GHz too. Measure your actual speed after fixing with our speed test.