I removed the CMOS battey (since the jumper is not included with my motherboard), waited and then remounted the battery and to my surprise, I was able to type the password at Bit Locker boot screen.
The solution is the following:
If you run an Asrock motherboard disable "Fast boot" in BIOS before starting BitLocker. Apparently with Fast boot enabled, the keyboard simply doesn't work at BitLocker boot screen. I tried with three keyboards and with a USB to PS2 adapter. My computer
is now perfectly running with BitLocker and Secure Boot enabled.
I also want to pay my respect to Gregg Carmack for his perseverance and suggestions.