The phone reports no SIM, or emergency calls only, and your mobile service has vanished. It looks serious and it is usually one of three things: the SIM has shifted in its tray, a contact is dirty, or the phone’s modem software has got stuck. All three are fixable in a few minutes.
The short answer
Restart the phone first, because a stuck modem process produces exactly this and a restart clears it. Then power off, remove the SIM tray, and check the SIM is seated properly and the gold contacts are clean. Between them those two steps fix most cases without a trip anywhere.
Why it happens
- The SIM has shifted in the tray. Trays hold SIMs loosely and a drop or even a firm knock can move one enough to break contact.
- Dirty or oxidised contacts. The gold pads on the SIM and the pins in the phone can tarnish, particularly in humid conditions.
- A stuck modem process. The phone’s cellular software can hang, and it reports no SIM because it cannot query it.
- A worn SIM. SIMs do age, particularly ones that have been moved between phones repeatedly.
- A software update. Updates occasionally break cellular configuration, and it is worth checking whether the timing matches.
- Physical damage to the tray or the reader. Usually after a drop, or after a tray inserted at an angle.
Restart the phone
A stuck modem process is a genuine and common cause. Restart before doing anything physical, since it takes a minute and resolves a fair share of cases.
Toggle airplane mode
On for fifteen seconds, off again. This forces the radios to reinitialise and re-register with the network, and it occasionally clears the state a restart does not.
Power off before removing the tray
Removing a SIM with the phone on can leave the modem in a confused state. Power down properly first.
Remove the tray and reseat the SIM
Use the supplied tool or a paperclip in the pinhole. Check the SIM is sitting flat in its recess and has not shifted. Refit the tray and make sure it goes in square and sits flush.
Clean the SIM contacts
Wipe the gold pads with a dry soft cloth. If they look tarnished, a pencil eraser used very gently cleans them well. Do not use liquid.
Check the tray for damage
A bent tray, or one that does not sit flush, means the SIM is not making contact. Trays are inexpensive and replaceable, and a bent one is a common consequence of forcing it in at an angle.
Test the SIM in another phone
The definitive test. If it works elsewhere, the SIM is fine and your phone’s reader or software is at fault. If it fails everywhere, the SIM has failed and your provider will replace it, usually free and usually the same day.
Reset network settings
This rebuilds the cellular configuration. You will need to re-enter Wi-Fi passwords afterwards, so it has a small cost, but it resolves corruption that nothing else reaches.
Never insert the tray at an angle or force it. The reader pins inside are delicate and bending them turns a SIM problem into a board-level repair. If the tray does not slide in easily, take it out and check the SIM is sitting flat rather than pushing harder.
Intermittent rather than constant
A SIM that works most of the time and drops out occasionally, particularly when the phone is knocked or put in a pocket, points at a mechanical problem rather than a software one. The SIM is making marginal contact, and the causes are a slightly bent tray, a worn reader, or a SIM that is not quite flat in its recess.
A practical and slightly inelegant fix that works: a very small piece of paper or tape on the back of the SIM, pressing it more firmly against the contacts. It is a stopgap rather than a repair, and it confirms the diagnosis before you pay for anything.
If the problem started immediately after a software update, check whether a carrier settings update is available. Restarting the phone prompts it to check, and these small updates fix cellular configuration problems that look like hardware faults.
eSIM specifics
If you use an eSIM there is no tray and no contacts, which removes most of the causes above and adds different ones:
- The profile has become inactive after an update or a device transfer. It usually needs re-downloading from your provider.
- The wrong line is selected if you have two profiles, one of which may be inactive or from a trip abroad.
- The profile was deleted during a reset. eSIM profiles are not restored by a backup and must be re-issued.
Worth knowing before a factory reset: deleting an eSIM profile can require your provider to issue a new one, so check the process before wiping the phone rather than afterwards.
Why does my phone suddenly say no SIM?
Most often a stuck modem process, a SIM that has shifted in its tray, or a dirty contact. Restart first, then reseat the SIM with the phone powered off.
Can a SIM card wear out?
Yes, particularly one moved between phones repeatedly or used for many years. Providers replace them free, usually the same day.
How do I know if it is the phone or the SIM?
Put the SIM in another phone. Working there means your phone is at fault; failing there means the SIM has failed.
It works then drops out when I move the phone. Why?
Marginal mechanical contact, from a slightly bent tray or a SIM not sitting flat. A small piece of paper behind the SIM confirms the diagnosis as a stopgap.
What if I use an eSIM?
There are no contacts to clean. Check the profile is still active and the right line is selected, and be aware that a factory reset can delete the profile and require your provider to reissue it.
The bottom line
Restart and toggle airplane mode before touching anything physical, since a stuck modem process is a common cause. Then power off, reseat the SIM and clean its contacts. Testing the SIM in another phone settles whether the problem is the card or the handset, and a provider will replace a failed SIM free and usually immediately.
