Phone Connectivity Troubleshooting: Wi-Fi Connected but No Internet, No SIM, and More

A phone showing full Wi-Fi bars but no working internet has a network problem, not a signal problem: the bars only measure the radio link between the phone and the access point, while actual internet access depends on everything past that link — the router’s upstream connection, the phone’s IP address and DNS settings, and any portal or VPN sitting in the path. The fastest way to fix any phone connectivity complaint is to first isolate whether the problem lives on this one device or on the network, then work the device-side basics (toggle the radio, forget and rejoin, restart) before touching anything deeper.

Signal bars are not internet

A smartphone reaches the internet over two independent paths: Wi-Fi and cellular data. Each path has two layers that fail separately.

The first layer is the radio link — the phone associating with a wireless access point, or registering with a cell tower. Signal bars describe only this layer. Full bars mean the phone can hear the access point loudly and clearly; they say nothing about whether that access point can reach the internet.

The second layer is everything behind the radio: the router’s connection to the Internet Service Provider (ISP), the Dynamic Host Configuration Protocol (DHCP) lease that hands the phone an IP address, the Domain Name System (DNS) servers that turn names into addresses, and any Virtual Private Network (VPN) or captive portal the traffic must pass through. When a user reports “full bars but nothing loads,” the radio layer is fine and the fault is in this second layer — which is why the symptom is categorized as a network or connectivity issue rather than a signal-strength issue.

Isolate first: one device, or the whole network?

Before changing any setting, answer one question: do other devices on the same network work?

• Other devices fail too → the problem is the network itself: router hung, ISP outage, upstream DNS failure. Rebooting the phone will not help; restart the router or wait out the outage.
• Only this phone fails (a classic help-desk scenario: the phone is dead on home Wi-Fi while laptops connect fine, and the same phone works instantly on cellular data) → the problem is on the device or in the device’s relationship with that specific network. This is where device-side troubleshooting starts.

That cellular-data check is a free diagnostic: if the phone browses normally the moment Wi-Fi is off, the phone’s networking stack, browser, and apps are all healthy, and the fault is scoped to the Wi-Fi path on that one network.

The “Connected, no internet” fix sequence

For a single phone that joins Wi-Fi but gets no internet, work least-invasive to most-invasive:

1. Toggle Wi-Fi off and on (or airplane mode on/off). This forces the phone to re-associate and request a fresh DHCP lease. It is the first thing to have a remote user try because it takes ten seconds and fixes a large share of cases.
2. Restart the phone. Clears a wedged network stack.
3. Forget the network and rejoin. This deletes the saved profile — stored password, any static IP or custom DNS the user (or a previous “fix”) left behind — and rebuilds it cleanly. Stale saved profiles are a leading cause of one-device-only failures.
4. Check for a captive portal. Hotel, café, and guest networks show “connected” until the user opens a browser and accepts the portal page. No portal acceptance, no internet.
5. Inspect device-specific settings: a static IP entered by hand, a manual DNS entry, a proxy, an always-on VPN that is failing, or a wildly wrong date/time (which breaks certificate validation and makes secure sites refuse to load). Because other devices at the same location work, these per-device settings are exactly where to look. The same static-IP and DNS pitfalls apply to desktops — see Windows network profiles and client connections.
6. Reset network settings as the last resort — this wipes all saved Wi-Fi networks, cellular preferences, and paired Bluetooth devices, so it costs the user real reconfiguration time.

”No SIM” and no cellular signal

When a phone reports “No SIM” or shows zero cellular service while otherwise running normally, the device cannot read its Subscriber Identity Module (SIM) or cannot register with the carrier. Reasonable first steps, in order:

1. Confirm airplane mode is off — it silently kills all cellular service.
2. Restart the phone. Re-initializes the modem and forces fresh carrier registration.
3. Reseat the SIM card. Power off, eject the tray, check the card for damage or corrosion, and reinsert it squarely. A SIM that shifted after a drop is a surprisingly common cause.
4. Test the SIM in another phone (or another SIM in this phone) to split “bad card” from “bad phone.”
5. Check with the carrier for an outage, a deactivated line, or — on newer devices — an eSIM profile that needs to be re-downloaded.

Escalate to carrier support or hardware repair only after these basics; the exam rewards the cheap, reversible step first.

Calls work but data doesn’t — anywhere

A distinctive pattern: no internet over Wi-Fi or cellular, yet voice calls and Short Message Service (SMS) texts flow normally. Calls and basic texts ride the carrier’s voice/signaling channels, which are separate from the packet-data path apps use. When both data paths die at once but voice survives, the culprit is almost always something on the phone that governs data globally:

• Mobile data toggled off plus a broken or unaccepted Wi-Fi network — the everyday cause.
• A data limit reached: the phone’s own data-usage cap, or a carrier plan cap that suspended data but not voice.
• A misbehaving always-on VPN or proxy that all data (both radios) is forced through.
• A misconfigured Access Point Name (APN) — the carrier data gateway settings — which kills cellular data specifically while voice registration still succeeds.

Symptom	Most likely area
Full Wi-Fi bars, nothing loads, other devices fine	This phone’s Wi-Fi profile or IP/DNS/VPN settings
Full Wi-Fi bars, nothing loads, all devices affected	Router or ISP upstream connection
”No SIM” / zero cellular bars	SIM seating, airplane mode, carrier registration
No data on Wi-Fi or cellular, calls and SMS fine	Data toggle, data cap, VPN/proxy, APN settings

How the 220-1202 exam tests this

• A scenario describes full signal bars with no page loads and asks you to pick the category of problem — expecting you to recognize it as a connectivity/network issue beyond the radio link, not a signal or hardware fault.
• A remote-work scenario where one phone fails on home Wi-Fi while every other device works, and asks what the user should try FIRST — the answer is always the quickest reversible device-side step (toggle Wi-Fi/re-join or restart), not router replacement or OS reinstall.
• A “No SIM” prompt asking for a reasonable first troubleshooting step — reseat/restart-level actions beat carrier escalation or hardware replacement.
• A pattern-recognition item: calls and texts work but no data on either radio — testing whether you know voice and data travel separate paths, pointing you at data toggles, caps, or APN/VPN configuration.

If the symptoms point toward data being deliberately throttled or capped rather than broken, see mobile data usage limits for how those caps behave. For where mobile troubleshooting fits in the exam as a whole, the full 220-1202 study guide maps all four domains, and 220-1202 practice questions make the reset-ladder reflex automatic.

Quick reference

• Signal bars measure only the radio link; internet failures with full bars are network/configuration problems.
• Always isolate: other devices failing = network problem; one device failing = device problem.
• First moves on a single failing phone: toggle Wi-Fi or airplane mode, restart, forget-and-rejoin the network.
• Forgetting a network wipes stale passwords, static IPs, and custom DNS stuck in the saved profile.
• Captive portals show “connected” but block traffic until accepted in a browser.
• “No SIM”: airplane mode off → restart → reseat SIM → test in another device → carrier.
• Calls/SMS working while all data fails points to data toggles, data caps, VPN/proxy, or APN settings — not the radios.
• Network-settings reset is the last resort; it erases every saved Wi-Fi and Bluetooth pairing.