How to Fix the the “Invalid SIM Card” Error on Android.If you’re getting an “Invalid SIM Card” error on your Samsung or other Android device, you’re probably having a bad day, unable to make calls or access the Internet.However, before you start thinking about ordering a new SIM (Subscriber Identity Module) card or – heaven forbid – start buying a new cell phone, know that this error is most often the result of software glitches rather than a hardware problem. At least it’s good news!
1. Reboot your Android phone
When this error occurs on your Android device, the first line of defense is a simple reboot. Shutting down and restarting often helps resolve minor glitches that cause this and other similar errors.In most cases, this is as simple as pressing and holding the phone’s power button until the restart option appears and then selecting it. However, the exact details on how to turn off or restart your phone may vary depending on your Android version or phone model.
If you need help with how to proceed, check out How to Turn Off Your Android Phone and you’ll learn more ways to turn off your phone than you need or ever wanted to know. Please!
2. Turn Airplane Mode On or Off
Airplane mode is a one-tap solution to turn Wi-Fi, Bluetooth, and mobile services on and off. As the name suggests, it’s designed to make it easier to comply with airline regulations regarding radio signals, but has also become an excellent troubleshooting tool.Sometimes switching airplane mode can solve network related problems. Go to your phone’s settings menu and turn on airplane mode. You can usually access Airplane mode by swiping the shade at the top of your phone screen and tapping the airplane icon.
Please wait a few minutes and then turn it off again. This gives your mobile network a mini-reboot, which can clear up minor connection issues.
3. Remove and reinsert the SIM card
A quick way to fix SIM card problem is to remove the SIM card from your Android phone and reinsert it.Turn off your phone, open the back cover and carefully slide out the SIM card tray. Inspect your phone’s SIM card and its slot for visible damage. If everything is ok, reinsert your device’s SIM card and turn on the power. 
Many newer phones no longer have a removable back panel, and the SIM card is accessed by removing the SIM card tray using a SIM card eject tool. One of these should have come with your phone, but if you’ve lost it, you can buy one online or at a cell phone store quite cheaply. As a last resort, you can use a paperclip or other blunt metal pin, but you risk damaging your phone if you’re not careful.
4. Correct network mode
Another common cause of the “Invalid SIM Card” error could be that your Android phone is set to the wrong network mode. Most phones offer GSM, LTE or automatic options. Selecting the wrong option may result in an invalid SIM card error.To fix this, go to the settings menu, select Mobile networks/connections (or similar), then Network. mode and finally select the correct option for your network provider. 
If you are roaming in another country, your phone may not support LAN mode. Sometimes purchasing a local SIM card is necessary for temporary use. Store your old card in a ziplock bag to avoid losing it. Roaming charges can be high, so it makes sense to use a local SIM card, which will only affect your phone number and text messages. Data-driven apps like Telegram or Whatsapp use internet data rather than cellular services.
5. Selecting a network manually
If your phone can’t automatically connect to the right network, manually selecting a network operator may solve the problem.In the Mobile networks section, select Network operators, then Search networksor uncheck Select automatically, which will initiate a search. 
Once available networks appear, select the correct one. Keep in mind that menu locations and names vary depending on the Android version and phone brand, so you may have to improvise a bit.
6. Reset network settings
Another potential solution is to reset your network settings. This action will not delete your data, but it will delete all Wi-Fi, Bluetooth, and cellular network settings, including saved networks and passwords.While typing all those passwords again is annoying, it may be necessary and is ultimately a harmless solution. Make sure you know the passwords or connection settings for critical networks, such as your work Wi-Fi network.Go to Settings > System > Reset > Reset network settings and confirm your choice. On our Samsung S22 Ultra test device, this option was located under System>General Management.
7. Boot your device into Safe Mode
By booting your Android device into Safe Mode, you can determine if a third-party app may be causing problems with your SIM card.In Safe Mode, all third-party applications are disabled. If your SIM card works correctly in this mode, the app is most likely to blame. You can then remove recently installed apps to find the problematic app.For detailed instructions, see How to Start Your Android Phone in Safe Mode.
8. Clear your phone’s cache
If you’ve been using your Android device for a while, it has accumulated a significant amount of cache. These temporary files can sometimes interfere with the system, causing errors such as “Invalid SIM card”.As a last resort, consider doing a factory reset. This step should only be taken after backing up all your important data as it will erase everything on your device and return it to its original settings.Before proceeding, make sure your data is securely backed up to a cloud service such as Google Drive, iCloud, or an external storage device. 
If you have a new phone with a built-in eSIM, you may be able to ditch the physical SIM cards altogether. Contact your service provider and ask if they support eSIMS on their network. If they do, follow their instructions.
What if all else fails?
Sometimes, despite your best efforts, the “Invalid SIM card” error still needs to be fixed. In such cases, it is worth checking if your device is blocked from the network or if there are problems with your IMEI (International Mobile Equipment Identity).
How to Fix the the “Invalid SIM Card” Error on Android
How to Fix the the “Invalid SIM Card” Error on Android