That card is the sdhc version of the original wood r4.something weird happened, i have this card R4 sdhc for DS, not the "i" version
when i put to to test it on 3DS, it didn't worked, i knew it wont work. but when i used the NTR flasher, it recognize it as r4isdhc card, and so i flashed it, of course it didn't worked.
after that i tried to reflash it again to NTRboot but this time the flasher didn't recognize it.
maybe the falsher was drunk?
It shouldn't even be flashable since it's not a dsi/3ds card. In any event, it certainly isn't supported.
However it might actually have a flashable bootloader since you managed to mess with it with ntrboot_flasher.
Go ahead and make an issue here
https://github.com/kitling/flashcart_core#requesting-support-for-a-new-cart
and maybe they can get it supported in the future.