Hi @arnavmalhotra
All the keys highlighted in the image you posted are connected in a matrix arrangement and connect to pins 64-66 of IC901 (see p.36 of the service manual you linked).
Unfortunately there's no circuit diagram of what the other side of the switches connect to.
It must be something common for all of them not to register when pressed.
Check if there's on earth (or voltage) on one side of each switch in the normal position