Marru_678

You can't truly "force" the boot sequence on Helios64 since U-Boot already checks SD, eMMC, and SATA. The SD card isn't bootable if the eMMC is still booting. Things to check quickly: SD must contain a properly written raw Armbian image (dd / balenaEtcher). You can't copy files. Check that it contains a bootloader and not simply an ext4 partition. Before starting, turn off the power completely (warm reboots might disregard SD). Once the computer has started, use lsblk -f to inspect the layout of the devices. On Helios64, the mmc numbering does change, therefore tools may conceal devices to save the live rootfs from being destroyed. If you want to be 100% sure, unplug the eMMC for a short time. If it boots, the SD is OK. The boot sequence isn't the problem; the SD image is.