- The order to check things in when a SIM is not recognized
- How to read SIM lock and carrier settings on iPhone
- Who to ask in eSIM and APN cases
The short answer
When your phone does not recognize its SIM, narrow it down in this order: your contract, the phone's settings, then the SIM itself. An iPhone may show Invalid SIM or No SIM Card Installed, and a Google Pixel may show No SIM. Many cases can be checked with a restart, turning the line on, and reinserting the SIM, but sometimes the SIM needs replacing or the phone needs repair. This article focuses on narrowing down the cause, not on how SIMs work, and it assumes phones used with carriers in Japan.
Three things to check first
- Is your contract active? Apple Support says to first confirm that you have a plan with a carrier and that it is active. If the contract was cancelled or payments stopped, the SIM will not work.
- Restart the phone. Try this once on both iPhone and Android.
- Is the line turned on? Google Pixel Help says No SIM can also appear when the SIM is inactive. Open Settings, then Network and internet, then SIMs, select your carrier's name, and turn on Use SIM.
Three things to check when it says "No SIM"
- Take it out and reinsert it
- Is the tray fully closed?
- Any dirt or damage?
- Is the phone SIM-locked?
- On iPhone, update carrier settings
Physical SIMs: the card and the tray
Apple Support advises removing the SIM from the SIM card tray, putting it back, and making sure the tray is fully closed and not loose. A SIM cut for another model or another maker's tray may not fit properly. Google Pixel Help advises wiping a dirty SIM with a microfiber cloth and asking your carrier for a replacement if it is damaged or bent.
For example, in a made-up case where you moved the SIM from your old phone straight into a new one, the fit in the tray is the first thing to suspect. If you have another SIM on hand, trying it shows whether the problem is the SIM or the phone.
SIM lock and carrier settings (iPhone)
| What to check | Where | What it tells you |
|---|---|---|
| SIM lock | Settings, then General, then About | If it does not say No SIM restrictions, the phone works only with its designated carrier |
| Carrier settings | The same About screen | A message appears if an update is available |
A SIM lock prevents a phone from using SIMs from companies other than the one it was bought from. How to check SIM lock on Android varies by model, so this article does not cover it. Check with the phone's maker or the company you bought it from. On the English iPhone interface, the wording may differ from the Japanese help page cited here.
eSIM and APN cases
If an eSIM, where the contract details are written onto a part built into the phone, is not recognized, Apple Support advises contacting your carrier. Because there is nothing to remove and reinsert, ask the carrier you have a contract with to check the setup.
The APN is the setting for where mobile data connects. According to Apple Support, some carriers require you to enter it when setting up mobile data, and on iPhone it appears under Cellular Data Network in Cellular settings. Entering wrong values can stop mobile data from working or lead to extra charges, so Apple advises not changing it unless your carrier tells you to.
If it is still not solved
If none of this helps, ask your carrier about reissuing the SIM or setting up the eSIM. If another SIM shows the same problem, ask about repairs: Apple for iPhone, and the phone's maker for Android.
Checklist
- Is your contract active, with payments up to date?
- Did you restart the phone?
- Is the line you use turned on?
- Did you reinsert the SIM and close the tray fully?
- Did you check SIM lock and carrier settings?
- Are your eSIM and APN set up as your carrier instructs?
One thing to check today
In your phone's settings, check that the line you use (SIM or eSIM) is turned on.