3DS Black screen, can't access HOME Menu

Not so long ago i bought two Nintendo 3DS which one of them don't work.

I don't know if it has a CFW installed or not, if its like the one that actually works in that case it only has FBI installed. None of the 3DS's i bought came with a SD card. I have a fully functional 3DS with FBI.

First it had the An error has occurred, hold down the POWER button to turn off the power screen, which i fixed by removing and installing the Wi - Fi card. Now everytime i turn it on it just black screens, if i press the POWER button again it goes to the Sleep Mode options, pressing the HOME menu freezes the console in the screen before the actual HOME menu, pressing the POWER button turns off the console.

I'm a noob in the 3DS hacking field, so please, if you know the solution of this problem try to explain things the easy way. i've tried a couple of things which none of them worked, i've never done any hardmod on it, just putting stuff that i see on tutorials in the SD card hoping it will work.

I've tried every system button combinations/shortcuts possible, including the updating

If someone knows how to fix this problem please, i would appreciate that A LOT