The Samsung Galaxy S21 supports dual SIM cards, and depending on the device model users can use either one Nano SIM and eSIM or two Nano SIMs and eSIM (dual standby). 

But the problem is, that a lot of users have reported issues with their Galaxy S21 dual SIM cards. According to these users:

• The device is unable to recognize either the first or second SIM card.
• Both SIM cards reset (network refresh and not recognized by the phone anymore) automatically after a period of time.
• When using the internet SIM cards reset automatically.
• A software update has caused the issue.

Most of the time the Dual SIM card issue on Samsung Galaxy S21 is caused by the SIM card reader, a hardware component responsible for reading/managing SIM cards.

However, there are instances where the dual SIM card issue arises due to a software issue. For those cases, you can apply Fix 01 to Fix 06 on your Galaxy S21 described in this guide (For hardware issues, look at Fix 07).

Note: Solutions in this guide will work on any Samsung Galaxy S21 model (S21, S21 Plus, S21 Fe, and S21 Ultra models.) 

Editor’s note: We created these instructions using a Samsung Galaxy S21 running Android 13. Depending on your device’s software version, some steps and menu positions may look slightly different.

Fix 01: Re-insert the SIM Card Correctly

If you are using a Nano SIM on your Galaxy S21 then you are experiencing dual SIM card issues because your phone may not recognize the SIM card due to incorrect insertion. 

For the physical SIM, you need to make sure that you have inserted it in the correct orientation in the SIM tray. Here’s how to do it:

1. Eject the SIM tray using the SIM ejector tool (you can also use a paperclip for this).
2. Place the SIM card on the tray. The gold contacts of the SIM should be facing downwards.
3. Now re-insert the SIM tray back into the device.

For the eSIM card, you can easily remove the current SIM card and re-add it by using the QR code provided by your network provider. If you don’t have the eSIM, simply contact your network provider and they will assist you in that matter and re-obtain the QR code for your eSIM card.

To remove and re-add the eSIM, follow the steps below:

1. Go to Settings.
2. Tap on Connections.
3. Then select SIM manager.

4. Tap on the eSIM card you want to remove.
5. Tap on the Remove button.
6. Confirm.
7. Once the eSIM card has been removed, restart your Galaxy S21. This gives your smartphone a fresh start to add the eSIM again.
8. Once the device has been restarted, again go to Settings >  Connections > SIM manager.
9. Now you will see a button “Add eSIM”. Tap on it to add your eSIM card once again.

After you have successfully added the eSIM card, restart your device once again to apply the changes successfully.

Fix 02: Reset Network Settings

Resetting network settings is a simple solution that can potentially fix the dual SIM card issue on your Samsung Galaxy S21. 

When you reset the network settings, it wipes all Wi-Fi, Bluetooth, APN, and mobile data connections, and returns them to their default factory settings, which can help resolve any glitches or issues that causing the problem.

Note: This process won’t delete any personal data or apps from your device.

Here’s how to reset network settings on your Samsung Galaxy S21:

1. Open Settings.
2. Tap on General management.
3. Then, tap on Reset.

4. Tap on Reset network settings.

5. Confirm.

Fix 03: Do a Software Update

If your problem is caused by a software bug or a previously installed software update, you need to update your Galaxy S21 once again because another update may have addressed the dual SIM card issue.

Here’s how you can update your device software:

1. Head over to Settings.
2. Tap on Battery and device care.

3. Then, tap on Software update.

4. Then, tap on Download and install.

Fix 04: Reset All Settings

The dual SIM card feature may not work if some accidental changes are made to the settings or an update has altered some settings. Resetting all settings on your device will potentially solve this issue as it brings all the settings back to their default state.

Here’s how to reset all settings on your Samsung Galaxy S21:

1. Navigate to Settings.
2. Scroll down and tap on General management.
3. Tap on Reset.
4. Then, tap on Reset all settings.

5. Confirm.

Fix 05: Clear the System Cache

The system cache is a storage partition on your device where frequently accessed data and processes are stored to retrieve quickly without reprocessing everything. It’s a helpful mechanism to reduce load times and lag. 

However, over time, this cache can become bloated with outdated data and lead to various issues, including the dual SIM card not working.

Clearing the system cache, also known as wiping the cache partition, is the fix needed to resolve these issues. Here’s how to do it:

1. Turn off your Galaxy S21.
2. Plug a USB cable into the device to power it up.
3. Then, press and hold the Power key + Volume up keys for a few seconds. When the recovery menu appears, release the keys.

1. Use the volume keys, highlight the Wipe cache partition, and press the power key.

1. On the confirmation prompt, select Yes and press the power key again.
2. Once the cache is cleared, you will see the recovery menu again. Use the volume keys, highlight the Reboot device now, and press the power key again.

Fix 06: Do a Factory Data Reset

If you’re still experiencing the dual SIM card not working issue after trying the previous solutions, and if this issue started after a software update, you need to do a Factory Data Reset to fix this problem (if the problem hasn’t occurred by a software update, please move to the Fix 07).

As you may already know, Factory Data Reset resets your device to its original factory settings by erasing all personal data, settings, and apps that you’ve added. This is why the factory data reset is often used to resolve persistent issues that seem to resist other fixes.

However, keep in mind that this will erase all your personal data from the device. So, back up all your important data before proceeding with this step.

Once you are ready, follow the below instructions to do a Factory Data Reset on your Samsung Galaxy S21:

1. Head over to Settings and then General management.
2. Tap on Reset.
3. Under the reset menu, tap on Factory data reset.

4. Enter the lock screen password, and then confirm.

Your device will restart and begin the Factory Data Reset process. You need to wait because this usually takes a few minutes. 

Once the process is complete, you have to set up your device as new. Then reconfigure your dual SIM settings and check if the issue has been resolved.

Fix 07: Take the Device to a Repair Center

As we mentioned at the beginning of this guide, the issue of your Samsung Galaxy S21 dual SIM card not working could be due to a hardware problem. 

This could be related to the SIM card slot or the internal SIM card reader that manages the SIM card functionality. If you’ve tried all the above fixes and your device still doesn’t recognize one or both of your SIM cards, you need to take your device to a Samsung repair center.

Remember to back up all your data before handing over your device for repair, as some repairs require a complete reset of your device.

Wrapping Up

That is it! So which solutions worked for you? We hope our guide helped you to resolve the dual SIM card issue on your Samsung Galaxy S21. 

If you have any further questions regarding this guide, feel free to leave a comment below. We will be there to help you.

Have a nice day!