"Choose an Operating System" - NO Mouse, No Arrow Keys

[Windows 10 Pro; Gigabyte GA-EP45-UD3P Rev 2.0 mobo; 8GB RAM; Team L3 240GB SSD.]

Both mice and my keyboard work perfectly after my system boots to the logon screen. My mice were definitely working perfectly about a month ago when I tested my desktop PC to make sure I could access my newly created entries of "Boot to Safe Mode" & " Boot to Safe Mode with Networking". Withing the past week or so, I enabled AHCI mode in my BIOS to take better advantage of correct "defrag"\TRIM for my O\S SSD. As best I can remember, that seems to have been the turning point after which my USB wireless mouse, my USB wired mouse, AND my USB keyboard arrow keys quit working when trying to choose a boot option. Since I can no longer make any boot selection with mouse or keyboard, I am stuck with booting only the default choice and only after the number of set seconds. Is there possibly a different BIOS setting that I must change or ??????

Thanks much for any potential help.

Thank you. I checked those two topics when changing to AHCI after I had already upgraded to Windows 10. I just re-read them. Nothing there seems to address my problem of "no mouse, no keyboard" where one would normally be able to select a boot option. I cannot select any option. The default is pre-selected and my system does boot as it should and runs as it should after booting. I have searched this forum (and the web) but I have been unable to find any info for my specific Win10 problem.