The complaint pattern is distinctive: the phone updated its system overnight, and in the morning the home Wi-Fi refuses, "failed to obtain IP address", "saved" but never connecting, or connecting then dropping every few seconds. Laptops and other phones in the house are fine. The phone is what changed, and the checks below run from most likely.

0. Restart both

Before anything: power the phone fully off (not just lock the screen) and back on; unplug the router for 30 seconds and plug it back in. A system update leaves old processes running until the phone truly restarts, and many "post-update bugs" end here.

1. Forget the network, rejoin

A Wi-Fi profile saved before the update may not match the new format. Settings → Wi-Fi → choose the network → Forget → rejoin by typing the password. If you don't remember it, see viewing saved Wi-Fi passwords on another device.

2. Random MAC address, the most common cause on routers with a device list

Android and iOS use a random MAC address per network for privacy. A system update sometimes generates a new random address, and if your router uses MAC filtering, an IP reservation for that phone, or per-device parental controls, the phone with its new address is treated as a stranger. Two options:

  • On the phone, for the home network only, switch to the device MAC: Android, Settings → Wi-Fi → gear icon on the network → Privacy → Use device MAC; iOS, Wi-Fi → (i) icon → turn off Private Address. Keep it random for public Wi-Fi.
  • Or update the router's list with the new address. Explained in what SSID, BSSID, and MAC address are.

3. "Failed to obtain IP address"

If that's the message, the phone has joined the Wi-Fi but the router isn't giving it an address. Besides the MAC issue above, the cause can be a full or conflicting router DHCP. Try a temporary static IP on the phone (advanced network settings): if it connects immediately, the problem is the router's DHCP, restart the router or widen its DHCP range.

4. New privacy settings enabled by the update

  • Private DNS / encrypted DNS (Android: Settings → Network → Private DNS; iOS via profiles). Updates sometimes turn this on, and on some networks, especially ones with a login page, it leaves the phone "connected, no internet". Set to Automatic or disable temporarily. Background in public DNS and privacy.
  • iCloud Private Relay / VPN re-enabled after the update. Turn off temporarily to test; see slow internet when using a VPN.
  • "Insecure network" detection: recent iOS and Android warn about old WPA/TKIP and sometimes refuse to join. That's not a bug, your router uses outdated security. Change to WPA2-AES or WPA3; see WPA2 vs WPA3.

5. A router that doesn't know the new standard

A freshly updated phone may now request WPA3, 6 GHz, or certain Wi-Fi 6 features, and an old router on old firmware answers wrongly. Symptoms: connects then drops repeatedly, or full signal with no internet. Two steps:

  • Update the router firmware. Many manufacturers release compatibility fixes a few weeks after a major Android/iOS release.
  • If the router uses WPA2/WPA3 mixed mode, try WPA2 only temporarily. Mixed mode on old routers is a frequent source of drop-outs for new phones.

6. Reset the phone's network settings

Not a factory reset. Android: Settings → System → Reset options → Reset Wi-Fi, mobile, Bluetooth. iOS: Settings → General → Transfer or Reset → Reset → Reset Network Settings. All Wi-Fi and Bluetooth profiles are cleared, data stays. This fixes profiles corrupted during the update migration, which "forget network" can't reach.

7. If everything fails: it really is a bug

Sometimes an update genuinely ships a Wi-Fi bug for a particular phone model or chip, it happens a few times a year on both platforms. The tell: many users of the same model complaining on forums in the same week. A fix usually arrives as a minor update within 1–3 weeks. Meanwhile, join the other band (2.4 GHz if you normally use 5 GHz, or vice versa), bugs often affect only one band, or use a hotspot from another device.

If the problem appeared without any update, the checks are different: see can't connect to Wi-Fi and Wi-Fi problems on one device.

Closing notes

Restart both → forget and rejoin → check the random MAC (especially if the router has a device list) → temporary static IP to test DHCP → disable private DNS/VPN/Private Relay → update router firmware and avoid mixed WPA mode → reset the phone's network settings. What's left is a bug waiting for the next patch.

Frequently asked questions

Why is only my phone affected, not other devices?

Because the phone changed, not the network. System updates often rotate the random MAC address, tighten privacy settings, or enable new standards an old router doesn't understand. Other devices didn't go through that change.

I've forgotten the network and rejoined, still failing. What next?

Reset the phone's network settings (not a factory reset). This clears all Wi-Fi, Bluetooth, and VPN profiles that may have been corrupted during the update, without deleting data. Then join again from scratch.