Turning off the WiFi was to check if the WiFi module became loose from the motherboard. o2DS will not boot or work correctly if it's not securely connected. You may still need to open it and look.
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- Take an SD card and copy everything off it onto a computer.
- Reformat the card as FAT32 + 32 KB cluster size with Windows File Explorer or guiformat.
- Check the (empty) card in a Full Write + Verify Test with H2testw. Do not skip this step.
- If the card passes, delete the *.h2w test files.
- If an error was reported, stop the test. Replace the faulty or fake card. Go back to step 1 or 2.
- A failed card can brick the o2DS in step 6.
- Build a test custom firmware setup. You may use the archive found here.
Assuming you don't have a backed up SysNAND *.bin image file because you bought this o2DS used.
6.
CTRTransfer with
Old 3DS or 2DS - 11.5.0 - EUR - CTRTransfer.