Assuming 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.
- Eject the SD from your console and insert into your PC.
- Load mset9.bat (if windows) or mset9.py (if linux) or mset.command (if mac).
- 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.
- Eject the original SD card from your PC
- PUT YOUR ORIGINAL SD CARD AWAY
- Insert your spare SD card into your PC
- Format the spare SD card as FAT32
- Insert the formatted, blank SD card into your console
- Return to Section I Step 1 of the MSET9 Guide.
- After Luma3DS installs and your console boots to the homescreen, power it off and switch to your original SD card for Finalizing.
- Backup your SD card to a folder to your PC (especially the Nintendo 3DS and DCIM folders)
- Double check that you properly backed up your data
- Do not skip the previous step
- Format the SD card as FAT32
- Insert the formatted, blank SD card into your console
- Return to Section I Step 1 of the MSET9 Guide.
- After Luma3DS installs and your console boots to the homescreen, power off your console
- Eject the SD from your console and insert into your PC
- Format the SD card as FAT32 again
- 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.