Hardware SD CARD REMOVED error with SD inside

[tranxuanthang]

If you test the SD and it's legit, and you're using an old 3DS, the problem might be the card slot.
Mine was doing the same thing, saying the sd card was removed, first when the system was moved too much, then just at random and later pretty much all the time, turns out the metal that holds the card in place was a little bent outwards and wasn't pressing the card against the contacts anymore. Fixed that and it's been working fine for over a year so far.

I think I have the same problem as you. Did you need to open (disassemble) the system to fix that?

 

[Edgarska]

I think I have the same problem as you. Did you need to open (disassemble) the system to fix that?

No, it's just the metal casing that keeps the card in place. Ideally, it should be perfectly straight, but if you insert and remove the card often it can bend a little, sometimes almost imperceptibly.
I just used a flat, very thin, screwdriver to bend it back into shape, just be careful not to bend it too much, and not to bend the actual pins. You don't need to insert the screwdriver too deep, it's just the first metal part you see.