Debian installation issue

[Linux for blind general discussion]

Hi all,

I installed Debian, the latest stable nonfree iso. I selected /dev/sdb 
as destination, with defaults and grub installation not to main 
destination, but I manually installed to the /dev/sdb, but now, I am 
unable to boot. I have Win 10 on /dev/sda and when I select the second 
hdd, it boots to the first. How can I install grub and have Windows on 
/dev/sda and Debian on /dev/sdb? When I install other distro and select 
sdb as destination and for grub, it works normally. I can reinstall it 
again, this sdb hdd is for Linux testing.

Thanks,

Pavel