boot – Help loading Ubuntu from Grub. Grub can’t find flash partiton


I installed Ubuntu on a partition of a MicroSD card on a laptop running Windows 10 on the internal drive. Attempting to boot to Ubuntu flashes i get grub in recovery mode
grub recovery mode

The problem is that ls command don’t show the flahcard hd1, only the internal hd0. Obiouvsly Grub can’t boot ubuntu.
Why?