ctrand won't mount sd card please help

[Pixie13]

Hi i just recently modded my 3ds and I'm not really tech savvy so I can't say i know exactly what I'm doing.
so my sd card won't mount and i keep getting an error that says error occurred sd card not mounted press any button to power off.
i don't know how to fix this and all i wanted to do was play games from my childhood.

if anyone could help by giving me step by step instructions on how to fix this problem I'd be forever grateful.

 

[G11dog]

Back up all of the sd's files, and format it again. Make sure it is formatted as fat32. For 32gb or smaller cards I think Windows' sd card formatter is fine. For windows' formatter make sure you back up your sd's files, right-click on your card and click format, format it as fat32 with the label as anything (3ds and Nintendo 3ds might cause problems) and quick format enabled. If it is larger than 32gb use guiformat (Edit: guiformat can be downloaded at http://ridgecrop.co.uk/index.htm?guiformat.htm ). When using guiformat, make sure you back up the sd's files, select your sd card's drive letter for "drive", "allocation unit size" should be 32768 for 64gb cards and 65536 for cards above 64gb, "volume label" can be anything (i think things like 3ds and Nintendo 3ds can cause problems), make sure Quick Format is selected, and click "start". After formatting copy all of the sd card files back on the card. If you get an error formatting make sure the read only thing on the side is pushed up. If formatting doesn't work I'd buy a new card or try a different card.