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SIM card suddenly shows no service after recent carrier update

Everything was working normally, then shortly after a carrier settings update or system update, the phone suddenly loses signal. The status bar switches to No Service, calls fail instantly, and mobile data disappears even though the SIM card was working fine before. Restarting the phone sometimes helps briefly, but the signal drops again.

This situation is more common than it looks. In most cases, the SIM card itself is not damaged. The issue usually comes from how the phone reconnects to the carrier network after updated carrier profiles, radio settings, or network authentication rules are applied. The device may still recognize the SIM, but it fails to properly register with nearby towers.

Confirm the SIM Is Still Detected

Start with a quick check before changing deeper settings.

  1. Open Settings.
  2. Go to Cellular or Mobile Network.
  3. Verify that your carrier name or SIM number appears.

If the SIM information is missing entirely, power off the phone and reseat the SIM card once. Dust or slight misalignment can sometimes cause registration failures after updates.

Toggle Airplane Mode to Force Network Re-Registration

Carrier updates can leave the modem stuck using outdated tower credentials. Resetting the connection often restores service.

  1. Turn on Airplane Mode.
  2. Wait about 30 seconds.
  3. Turn Airplane Mode off again.

Watch the signal indicator for a minute. The phone should renegotiate with the network and regain service.

Manually Reconnect to the Carrier Network

Automatic network selection sometimes fails after carrier configuration changes.

  1. Open Settings → Cellular → Network Selection.
  2. Disable Automatic.
  3. Wait for available carriers to load.
  4. Select your carrier manually.

If service returns, you can switch Automatic back on afterward.

Reset Network Settings

This step clears cached carrier data, saved towers, and modem configuration without deleting personal files.

  1. Go to Settings → General → Transfer or Reset (or System → Reset on Android).
  2. Select Reset Network Settings.
  3. Restart the phone when prompted.

Wi-Fi passwords will need to be reentered, but this often resolves update-related signal loss immediately.

Check for a Second Carrier Update

Carriers sometimes release follow-up patches when widespread connection issues appear.

  1. Open Settings → General → About.
  2. Wait for a carrier update prompt.
  3. Install it if available.

Test the SIM in Another Phone

If possible, insert the SIM into a different unlocked device. If it connects normally, the problem is local to your phone’s network configuration. If it also shows no service, the carrier may need to reprovision the line.

Optional: Request Carrier Re-Provisioning

Contact your carrier and ask them to refresh or reprovision your SIM on their network. After large updates, account-side registration sometimes becomes mismatched with the device profile.

Once the phone successfully reconnects and signal bars remain stable, the issue is resolved.