It’s apparent it sees the SD card, but it’s not seeing the MBR on it. I doubt the DOS version is the issue, because it’s not event attempting to boot. Unfortunately there’s no guarantee your 360kb floppy drives are in working order if you don’t know already. I usually recommend a flash floppy but for an machine like this you’re really getting into the weeds with it not being bootable. Try an different SD card, they can be weird, smaller is better. And try writing a different dos bootable image to it.