I never downgraded my 3DSDid you downgrade From GW Menu in the past ?
if so read the faq of Luma3DS.
I had trouble with Luma3DS, switching from AuReiNand. BlackScreen on Luma3DS but it worked on AuReiNand so i red the faq to solve my preoblem. It was the downgrade from GW Menu.
https://github.com/AuroraWright/Luma3DS/wiki/FAQ-and-Troubleshooting
I've tried already to formatt Emunand and my SD card and tried CFW's like Rxtools, Luma, ReiNAND, AuReiNAND, miniPASTA...
Only miniPASTA worked in SysNAND, the others just blackscreen.
And in Luma3DS I never get the Config menu