My R4 3DS SDHC Gold Pro stopped working back in May 2019, and I kind of left it sitting since. Now, I’d like to use it,...

Programming the circuit boards isn’t the problem — It’s either the SD CARD, or you 3DS Internal Memory(System Memory.) Also, you 3DS has CFW… One of the problems occurring with CFW, could be if you installed the dsiware-hack “Haaaaaaxxxxx”. My 3DS bricked(3 of them) before my 4th worked, so… Oh, right: Have you been using R4, or TWLOADER/TWILIGHT-MENU? That could be the problem. My 3DS wouldn’t boot the whole time they were on there, so I used GODMODE9(or a different program) to programmatically delete them. After that, I practically let my 3DS DIE(Battery-Drain), and then re-charged it. After it was at 100%, I pressed the POWER BUTTON, and it booted up just fine. Glad I could help, Momoro