Do you mean that none of the buttons? on the left side multi media board below the Power button are working and that you cannot enable or disable the touchpad or anything else using those buttons?.
Here’s an image taken from the service manual for the laptop that shows the buttons, including the touchpad enable/disable button, that I mean.
(click on image to enlarge for better viewing)
You may have to check if the left multi media board cable is securely connected at both ends, media board and motherboard in the laptop.
Go to p.80 in the manual to check where to find it.
If the media board is faulty, I cannot find a replacement board when searching online using the part number, (part #55.BCR01.003). All the suppliers say NLA (No Longer Available). You may have better luck
In the meantime to be able to use the laptop, connect a USB mouse to navigate through the laptop.
What OS is installed in the laptop, Win XP, Win 7, Win 10 etc?