Short answer: split the symptom before you touch anything. A network that never appears in the list is a signal, band, or broadcast problem. A network that appears but will not join is a credentials, addressing, or clock problem. They have almost no fixes in common.
The split, and what each half means
| What you see | What it points at | First move |
|---|---|---|
| The network is absent from the list; other devices see it | Band mismatch (5GHz/6GHz range), hidden SSID, or a router that has stopped broadcasting | Move closer, then try Join Other and type the name |
| The network is listed; tapping it does nothing | Password changed on the router, or a captive portal never completed | Forget the network, then join again |
| It joins, then shows no internet | The link is fine — this is upstream (the router's own connection) | Test another device on the same network |
| It joins, then drops within seconds, repeatedly | Address conflict, Private Wi-Fi Address being refused, or an unstable band | Turn Private Wi-Fi Address off for this network as a test |
| A "weak security" or certificate warning appears | The router's encryption mode, or a wrong date on the phone | Check Settings → General → Date & Time is automatic |
Working out which row you are in takes about a minute and is the difference between a fix and an hour of random toggling.
Networks that never appear
Band first. 5GHz and 6GHz travel less far than 2.4GHz and are worse at passing through walls. If your router publishes separate names for the bands and you are two rooms away, the 5GHz name may genuinely not reach you while a laptop in the same room finds it easily. Walk towards the router and watch the list.
Hidden networks do not appear in a scan at all by design. You have to tap *Other…* and type the exact SSID, including capitalisation. A hidden network is also a common reason a phone "loses" a network it used yesterday: it is not lost, it just is not broadcast.
A router that stopped broadcasting. This is common and easy to misread, because the router's wired side and its admin page may both still work perfectly. Restart the router and watch whether the name comes back.
A phone-side scan problem. Toggling Wi-Fi off and on rebuilds the scan, and it is worth exactly one try. If turning Wi-Fi off leaves the toggle greyed out, that is a different and more serious symptom — see the note on the phone side below.
Networks that appear but will not join
① A password that changed. If someone changed the router's Wi-Fi password, the phone keeps offering the old one and the router keeps refusing it. There is no useful error message. Forget the network in Settings → Wi-Fi → ⓘ → *Forget This Network*, then join again and type the new password.
② A captive portal that never completed. Hotels, airports, cafés and trains do not authenticate with the Wi-Fi password alone; they need a web login. If the login page never appeared, open a browser and request any plain http:// address, or open the network's ⓘ page and check for a *Sign In* option. A portal that was never finished leaves the phone believing it is associated while nothing works.
③ A wrong date and time. Secure networks validate certificates, and certificate validation depends on the clock. If the phone's date is wrong — a dead battery, a long time powered off, or a manual time setting — the network can refuse the connection for reasons that have nothing to do with the password. Set Settings → General → Date & Time → Set Automatically on.
④ Private Wi-Fi Address. The phone presents a random address per network instead of its hardware address. That is good privacy, and it breaks any network with a per-device allow list: MAC filtering on a home router, or a corporate or hotel network that registers devices. It is per network, so one network can be failing on this while every other one works. As a test, set it to *Off* for that network — under the network's ⓘ — and join again.
⑤ A static address or a stale proxy left over from somewhere else. Both are stored in the network profile and both survive a password change. Forgetting the network clears them, which is the reason forgetting works when tapping does not.
The order that wastes the least time
- Forget the network and join again. One step, clears credentials, Private Wi-Fi Address choice, static addresses and stale proxies.
- Check the date and time are automatic. Ten seconds, and it rules out the class of failures that look like a wrong password.
- Try Private Wi-Fi Address off for that one network, and retry.
- Restart the router if no device can join. If other devices join fine, the router is not the problem.
- Restart the iPhone. It rebuilds the Wi-Fi stack without deleting anything.
- Reset network settings —
Settings → General → Transfer or Reset iPhone → Reset → Reset Network Settings— only as a last resort, because it deletes every saved Wi-Fi password and every Bluetooth pairing on the phone.
Apple's own guidance for a Wi-Fi connection that fails covers the settings side of this list. What Apple does not publish is any figure for how long a Wi-Fi join should take, so treat any specific timeout you see quoted as an estimate rather than a specification.
When it is the phone
A phone-side fault has a distinctive shape: every network fails, including ones that worked yesterday, on both bands, and the Wi-Fi toggle is greyed out or the list never populates at all. Restart the phone first. If the toggle stays unavailable, that is a hardware or service question rather than a settings one, and it is the point to have the phone checked rather than continuing to reset things.