Open the computer and remove the CMOS and system batteries.
After removing the batteries, press the power button for about 1 minute.
Reinsert the battery, reassemble the computer and start it up regularly.
Enter the Bios, readjust all settings and save them.
The keyboard should now work properly
Here is a video on how to open the computer, keeping in mind that if you open it under warranty, you will lose it.