When mobile data is not working, start with the simple checks, because they are the ones Apple and Google put first. Most of this page is their own troubleshooting lists, in their order. The APN, the setting people usually blame, is on neither company’s main list, and we explain when it does matter.

On an iPhone

These are Apple’s steps for a phone showing SOS, No Service or Searching, from Apple’s support page.

  1. Turn on Airplane Mode for at least 15 seconds, then turn it off.
  2. Restart the phone.
  3. Check with your carrier that your account is active and in good standing, that there is no outage, and that the phone “isn’t blocked or barred from receiving cellular services”.
  4. Update iOS.
  5. Check for a carrier settings update. Connect to Wi-Fi, then open Settings, General, About. If an update is available, the phone offers it.
  6. If the line itself is off, which can happen with two SIMs, tap Turn On This Line.

Before any of that, make sure the switch is on. Settings, Cellular, Cellular Data.

Step 5 matters most after changing carrier. Apple says, “If you insert a new SIM card into your iPhone or iPad, you need to download the carrier settings for your new carrier.”

On an Android phone

These are Google’s steps for a Pixel, from Pixel Phone Help. Other Android phones use similar menus with different names.

  1. Open Settings, tap Network & Internet, then SIMs. Make sure Mobile data is on.
  2. Tap your carrier’s name and make sure Use SIM is on.
  3. Make sure airplane mode is off.
  4. Turn off Wi-Fi, so you can tell whether the mobile network is working.
  5. Check that the SIM is activated and inserted correctly. Try another SIM if you have one.

When it is the APN

The APN, or access point name, tells a phone how to reach the carrier’s data network. Phones bought from your carrier get it automatically. It becomes the suspect in one situation: you put a new carrier’s SIM in a phone you already owned, calls and texts work, and data does not.

Then the fix depends on the phone.

On an iPhone you usually cannot edit the APN. Apple says you can view or edit it only “if your carrier allows it”. The carrier settings update in step 5 above is how an iPhone gets the right values.

On Android you can enter it by hand, under Access Point Names in the mobile network settings. Use your carrier’s own values. We list them in APN settings, and what is an APN explains the fields.

Google’s advice for a phone whose settings have been changed is to go back: “reset your APN settings to default.”

After a software update

Apple says that updating iOS “resets any changes made to your APN settings”, unless they came from a configuration profile. If you had typed in an APN and data stopped after an update, that is why. Enter it again.

When it is the carrier, not the phone

If none of this works, look at the account. Apple’s third step is the one to repeat: confirm with your carrier that the account is active, that the phone is not blocked, and that it “is set up with the right data plan”.

If the data works and only picture messages fail, that is a different problem. See MMS not sending.

  • troubleshooting
  • mobile data
  • APN settings