I am having some difficulties with unlocking my number- keyboard on the right side. I have already tried multiple times pressing the Number Lock button, including the 'PrtScr' button and the 'Fn' button alongside the Number lock and the 'PrtScr' button. However I still can't use the number key board.
The numlock key should be cleaned, all around, using compressed air, if that does not work, the circuit may have oxidized. A technician can remove the key and clean the circuits. Last but not least if the last two solution don't work a keyboard replacement may be required.
Anyway, it's not a big issue. I always have my numlock key on, I never turn it off.