I hade the same problem as you and it was becouse i had downgraded trough the gateway menu.
This solved the problem for me https://github.com/AuroraWright/Luma3DS/wiki/FAQ-and-Troubleshooting#i-get-a-black-screen-on-boot-with-an-old-3ds-which-has-been-downgraded-from-the-gateway-menu-in-the-past
since it will just use the original msgid.
Swedish for Rev648
http://www.badongo.com/file/16182306
Fully updated to Rev648
Added pirateX changes and translated the new phrases.
Hiya guys here is an update to the swedish language file it has been updated to Rev570
and some minor spelling/grammar fixes also translated the new phrases.
Swedish Rev570
http://www.badongo.com/file/15778754