As
Stovepipes as said, resetting the CMOS cleared all motherboard settings to default.
Regarding getting into the BIOS, some mobos need you to be super quick pressing the appropriate key during POST e.g. on my (old) Asus it's F8 which sometimes doesn't work at first boot. Also, make sure keyboard is plugged in ok. Unplug any unnecessary USB devices for now.
& if you don't have already, you an pick up the motherboard's manual
here