The problem appears to be that you're using an old version of Luma3DS, as previously stated. Follow this guide to fix the problem:
https://3ds.hacks.guide/updating-b9s
If you can't get it to work, put v7.1 of Luma onto the root of your SD card, or put the B9S installer firm directly on the root of your SD card and rename it boot.firm.
renaming the installer to boot.firm was something I thought of, but I didn't suggest it for some reason.