I kinda see what's the problem then...If you're putting the files on your R4 then that's your problem. The 3DS has an internal SD card.
I have a micro 32gb card that's why I was using a R4 so it could fit into my 3ds xl... but I think I know what the problem is... hopefully it now works though.You suppose to be using the sd card in the 3ds...
Also don't follow videos. Only follow 3ds.guide
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actually the video I was following was posted just about this weekinb4 he bricks following an outdated youtube video