I couldn't boot Guix installed on nvme m.2

[Tomás Chapunov]

Hi! I have a debian installation on a Ssd disk. I have a second 1tb hard
disk. I have an Msi b250 gaming pro mother.
Now I installed an 256 GB nvme m.2. It works.

So I installed Guix there from the graphical install. Guided without
encryption. And selected GPT partition during installation. It all worked,
it installed on the disk.
But when I reboot, and select that disk for booting, it returns a text
message that says that the disk is not bootable. So it stays struck there.
What does I have to check? Did I make something wrong, missed any step?
Maybe a grub issue?
Thanks!

Tomas Chapunov