If you already tried that and the problem is still there, call Gigabyte and ask them for help.
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Select spain for your country, you may have to do email support if they have no phone support.
The only other way to verify the system is seing your total amount of memory,
Try a live linux distro suse is what I want you to use, it'll replicate the windows environment so it will be easy to navigate through.
https://software.opensuse.org/132/en