Keyboard access on bios boot

I have installed a M.2 500gb drive in my gigabyte motherboard. The aim is to transfer two of my multi boot Windows 10 OS to this drive and delete the same two on the main hard drive used before. SO far so good without the 'Old hard drive ’ attached I have divided the m.2 into two drives installed W10 to both and all is well.
The issue arises when I attach the old drive as well and try to access the multi boot menu (in BIOS?) but the keyboard will not now respond so I can select the Boot option I want. I also get 5 fast beeps on start up. This I thought I had sorted by telling BIOS originally to Ultra Fast Boot.
Without access to the selection screen of the multi boot options I can only access the first boot sector.
Any help would be appreciated