If you are experiencing the "System Settings loading infinitely after reinserting the SD card" error when trying to install MSET9 using the PC (cli) or Play Store guide, this page will help you resolve that issue by using a blank SD card to perform a fresh install with either a spare SD card, or your original SD card which has been backed up and formatted to avoid issues caused by your current install.
It also works if you aren't getting the Mii Maker entry at the Extra Data screen.
All of your original games and saves will be intact as long as you follow the steps properly.
Before continuing please ensure you are choosing the right model (old 3DS, old 3DS XL, old 2DS vs New 3DS, New 3DS XL, New 2DS XL) and correct system version.
Also please make sure you are injecting AFTER ejecting from the extra data screen and not before.
NOTE: If your Extra Data has crashed at Section II Step 5 and you never saw the mii maker icon, you injected early. Follow the steps below to remove MSET9 and try Section II again.
Instructions
Follow these steps first to remove MSET9:
Power off your console (if your 3DS is stuck at the extra data screen with a spinning circle, force power off your console by holding the power button down for 15 seconds)
Insert your SD card into your PC
Run the MSET9 script:
Windows: Double-click mset9.bat
macOS: Double-click mset9.command and enter your password if prompted
Linux: open a Terminal window, cd to the root of your SD card, then type python3 mset9.py and press Enter
Choose model then press 3 to remove MSET9 and then press enter to close the script
Choose option below based on if you have a spare SD card or not
Power off your console (if your 3DS is stuck at the extra data screen with a spinning circle, force power off your console by holding the power button down for 15 seconds)
Insert your SD card into your phone/tablet/computer
Run the MSET9 Installer application
If Remove MSET9 is not highlighted:
Tap on Select "Nintendo 3DS" Folder, then navigate to your <code<Nintendo 3DS folder on your SD card
Once inside the Nintendo 3DS folder, tap on “Use this folder”, then “Allow” if asked
Tap Remove MSET9
Proceed to the Play Store SD tab below
Eject the original SD card from your PC
PUT YOUR ORIGINAL SD CARD AWAY
Insert your spare SD card into your PC
Make sure this is your spare SD card and not the original SD card
Restore your backed up folders to the SD card and continue on to Restoring / Updating CFW to ensure you have Luma on your SD card, and then continue onto Finalizing.
SD Formatting does not work properly on Android phones or Chromebooks so this guide only allows for the use of a spare SD card already formatted with FAT32 if using the Play Store Method. Tip: 32GB SD cards or smaller are FAT32 by default. If you do not have a spare SD card in the FAT32 format you will need to use a PC and use one of the other tabs in this section
Eject the original SD card from your phone/tablet/computer
PUT YOUR ORIGINAL SD CARD AWAY
Insert your spare SD card into your phone/tablet/computer
Make sure this is your spare SD card and not the original SD card
Delete everything from the SD card (Do not copy your data back to the card yet)
Insert the blank SD card into your console
Return to Section I Step 1 of the MSET9 Play Store Guide and complete every step up to the bottom of the page.
After Luma3DS installs and your console boots to the homescreen, power it off and switch to your original SD card for Finalizing
