How to Fix a Phone SIM Card Not Detected Error

Published 2026-10-16 · Marion Phone Repair

Your phone suddenly shows No SIM Card Detected, Invalid SIM, SIM Card Error, or No Service even though the SIM card is inserted. You cannot make calls, send texts, or use mobile data. The phone may show an empty signal bar or an exclamation mark where the carrier name should be. SIM card detection failures can happen suddenly after a drop, software update, or for no apparent reason — and the fix is usually either reseating the SIM, updating the phone, or addressing a carrier-side issue.

Restart the phone first

A restart reinitializes the cellular modem and SIM card reader. Many temporary SIM detection failures are fixed by a simple restart:

Enable Airplane Mode, wait 30 seconds, then disable Airplane Mode. This forces the phone to disconnect from and reconnect to the cellular network without a full restart
If the Airplane Mode toggle does not fix it, do a full restart: hold the power button, select Restart, and wait for the phone to boot completely. Give it 30 to 60 seconds after boot to detect the SIM and connect to the network

Reseat the SIM card

The SIM card may have shifted in the tray or have a poor connection with the reader contacts:

Power off the phone completely
Locate the SIM card tray (usually on the side of the phone). Use the SIM eject tool (included in the phone's box) or a straightened paperclip to push into the small hole next to the tray. The tray pops out
Remove the SIM card from the tray
Inspect the SIM card for visible damage: scratches on the gold contacts, chips or cracks in the plastic, or bent edges. Minor scratches are normal and usually do not cause problems. Deep gouges or cracks can break the circuit
Clean the gold contacts on the SIM card with a soft, dry cloth. If there is visible oxidation (tarnishing on the gold contacts), gently clean with a pencil eraser, then wipe with the cloth
Place the SIM card back in the tray, making sure it is properly aligned (the notched corner matches the tray shape). Make sure the SIM sits flat in the tray and does not ride up on one side
Slide the tray back in firmly and power on the phone

Try the SIM in another phone

This is the most important diagnostic step because it tells you whether the problem is the SIM or the phone:

Put your SIM card in a different phone. If it works in the other phone, the problem is with your phone's SIM card reader, software, or settings
Put a different known-working SIM card in your phone. If the other SIM works in your phone, your SIM card is damaged or deactivated — contact your carrier for a replacement
If neither SIM works in your phone, the phone's SIM card slot or modem has a hardware issue

Check for SIM card size mismatch

Modern phones use nano-SIM (the smallest size). If you transferred a SIM from an older phone using an adapter, the adapter may not make proper contact:

Adapters can be slightly too thick, preventing the tray from seating fully, or they can misalign the SIM's contacts with the reader pins
If you are using a SIM adapter, visit your carrier store and get a properly sized SIM card for your phone. Most carriers will swap SIM sizes at no charge

Software troubleshooting

Check for carrier settings update

iPhone: Settings, General, About. If a carrier settings update is available, a popup appears. Install it. Carrier settings updates include changes to how the phone communicates with the network and can fix SIM detection issues
Android: These updates are usually applied automatically through system updates. Check Settings, System, Software Update

Reset network settings

This is the most effective software fix for SIM detection issues. It resets all network configuration to factory defaults:

Android: Settings, System, Reset, Reset Network Settings. This resets Wi-Fi, Bluetooth, and cellular settings. You will need to reconnect to Wi-Fi networks and re-pair Bluetooth devices
iPhone: Settings, General, Transfer or Reset, Reset, Reset Network Settings
After resetting, restart the phone and wait for it to detect the SIM and connect to the carrier. This can take up to 2 minutes

Check SIM lock status

If you bought the phone from one carrier and are trying to use a SIM from a different carrier, the phone may be carrier-locked. A locked phone shows Invalid SIM or SIM Not Supported when a SIM from a different carrier is inserted
Contact the original carrier to request an unlock. In the US, carriers are required to unlock phones after the device payment is complete. Once unlocked, the phone accepts SIM cards from any compatible carrier

Update the phone software

Outdated firmware can have bugs that affect SIM card detection, especially after a carrier network upgrade
Settings, System, Software Update — install all available updates. Some SIM detection fixes are included in security patches, not just major OS updates

Carrier-side issues

Sometimes the problem is on the carrier's end, not the phone:

SIM card deactivated: If you recently switched plans, ported your number, or your account has a billing issue, the carrier may have deactivated the SIM. Call your carrier's customer service from another phone to check
Network outage: A local network outage can make the phone show No Service or SIM Error. Check your carrier's website or social media for outage reports in your area. If neighbors or family on the same carrier also have no service, it is an outage
SIM card expired: Prepaid SIM cards that have not been used or recharged within a certain period (usually 60 to 90 days) are deactivated by the carrier. Contact the carrier to reactivate or get a new SIM
IMEI blocked: If the phone was reported lost or stolen (even if you bought it used and it was reported by the previous owner), the carrier may have blocked the IMEI. Check at imeipro.info or contact the carrier with the IMEI number (found in Settings, About Phone)

eSIM issues

If your phone uses an eSIM (embedded SIM) rather than a physical SIM card:

An eSIM cannot be physically reseated, but it can lose its configuration. Go to Settings, Cellular (iPhone) or Settings, SIM Cards (Android) and check that the eSIM line is enabled
If the eSIM is not showing at all, it may need to be reprovisioned. Contact your carrier — they can send a new eSIM activation remotely (via QR code or carrier app)
Some dual-SIM phones have both a physical SIM and eSIM. Make sure the correct one is set as the active line for calls and data

Hardware SIM reader failure

If no SIM card works in the phone (you tested with a known-working SIM) and software resets did not help:

The SIM card reader (the spring-loaded contacts inside the SIM slot) may be damaged. This can happen from inserting the SIM incorrectly, inserting the tray with too much force, or from a drop that bent the internal contacts
Inspect the SIM slot with a flashlight. Look for bent pins, debris, or corrosion inside the slot
Do not attempt to straighten bent pins yourself — the contacts are very small and fragile. Professional repair is recommended

SIM card repair in Marion

If your phone shows SIM card not detected and the troubleshooting above did not fix it, Marion Phone Repair can test the SIM card reader, clean corroded contacts, repair bent pins in the SIM slot, and diagnose whether the issue is the SIM card, the reader hardware, or the phone's cellular modem.