SIM Card Not Working? Is It the SIM or Your Phone?

Key takeaways

• A SIM card not working is usually due to a loose or dirty SIM card, a phone glitch, a new SIM card that hasn't activated yet, or an account or network problem. Restarting the phone and reinserting the SIM card fixes most cases.
• Plugging the SIM card into a second phone shows where the fault is. If the SIM card works there, the original phone is the problem. If it doesn't, ask the network for a replacement.
• If service drops suddenly for no obvious reason, or a new SIM card still has no service after 24 hours, contact the network that issued the SIM card.

 

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Phone showing "No SIM" or losing its signal for no obvious reason? This guide helps you work out why, step by step, starting with the quickest fixes.

Why is my SIM card not working?

The message on your screen is the best clue. The wording varies slightly between phones, but these are the usual ones.

What you see	What it usually means	Try this first
No SIM or SIM not detected	The phone can't read the SIM card, often because the card has shifted in the tray or is dirty.	Restart the phone, then remove and reinsert the SIM card.
Invalid SIM or SIM failure	The phone can read the SIM card but can't verify it, which can point to a damaged or inactive SIM card.	Test the SIM card in another phone, then contact the network if it fails there too.
No service or Searching	The SIM card is fine, but the phone can't find a signal because of a local outage or a phone setting.	Turn airplane mode on and off, then check the network's status page.
Emergency calls only	The phone has found a mobile network but can't connect to your plan, so only emergency calls work.	Restart the phone, then contact the network if the message stays.
SIM not provisioned or not activated	The SIM card hasn't been set up on a network yet, or the account has a problem.	Wait a few hours if the SIM card is new, then contact the network.
SIM PIN or PUK required	The SIM card has locked itself after too many wrong PIN attempts.	Ask the network for the PUK code, and don't guess, because too many wrong PUK attempts can block the SIM card for good.

How do I fix a SIM card that isn't working?

Work through these in order. Each one takes a minute or two.

1. Restart your phone. Obvious, yes, but it works more often than anyone likes to admit.
2. Turn on Airplane mode, wait ten seconds, then turn it off. Airplane mode is also called Flight mode on some phones. This prompts the phone to search for a network again.
3. Install any pending software update. Updates often include fixes for network problems.
4. Remove and reinsert the SIM card. Switch the phone off, then open the SIM tray with the ejector tool (a straightened paperclip works if the tool has wandered off). Wipe the SIM card and tray with a dry, soft cloth, then put the card back flat and snug.
5. Check that the SIM is switched on. On a dual-SIM phone, you can turn off a SIM in settings, or set mobile data to the other SIM.
6. Reset network settings. This clears saved WiFi networks, Bluetooth pairings and mobile settings, but not your photos, apps or messages. The menu name varies by phone, so search for "reset network" in Settings. Write down your WiFi password first.

Using an eSIM instead of a physical SIM card? The first few steps still apply, and our guide to fixing an eSIM that isn't working covers the rest.

Is it the SIM card or your phone?

If the quick fixes haven't worked, a second phone settles it. Switch both phones off, move the SIM card across, then switch the second phone on.

• The SIM card works in the second phone. The original phone is the problem. Check for updates, reset its network settings, or ask the phone's maker to look at it, especially if it has had a drop or a splash.
• The SIM card doesn't work in the second phone either. The SIM card is faulty or inactive, and the network can replace it. Visible scratches, bends, or a cracked edge point the same way.

What if your new SIM card isn't working?

New SIM cards often need activating first, and that isn't always instant. Check the instructions that came with the SIM card, then give it a few hours. Activation usually takes a few hours, but it can take up to 24.

A few other things catch people out:

• Your old SIM card stops working once the new one activates. That's normal, not a fault.
• The new phone is locked to another network. A locked phone won't accept your SIM card. The network that sold the phone can unlock it, usually for free.
• The SIM card is the wrong size. A SIM card that doesn't sit flat in the tray won't be read.

If SIM problems keep happening

If you're on SMARTY, our Network Status Checker shows whether there's a problem in your area, which is worth checking before you take your phone apart. If you've worked through the steps and the SIM card still isn't working, get in touch with SMARTY Customer Care and tell them what you've already tried.

Switching networks won't fix a damaged phone. But if the same SIM problems keep recurring with your current provider, a SMARTY SIM-only plan is worth a look.

SMARTY SIM-only plans have no contract. The data options run from 5GB up to unlimited, so you can pick what you'll actually use. You can get a physical SIM card in the post, or an eSIM if you'd rather get started quickly.

FAQs

Why is my SIM card not working all of a sudden?

A SIM card usually stops working suddenly because of a phone software glitch, a SIM card that has shifted in its tray, a network outage or an account problem. Restarting the phone and reinserting the SIM card fixes most cases. If neither helps, the network that issued the SIM card can check the account and replace the SIM card if needed.

How long does a new SIM card take to activate?

A new SIM card usually activates within a few hours, though activation can sometimes take up to 24 hours. If a new SIM card still shows no service after a day, call the network that issued it.