It isn't software. RIP keyboard, probably. However....

Did it ever work for you or is it a new-to-you machine? Does pressing really hard make it work? If the latter, then there may be a dirty connection.

If not, then since the keyboard is toast as it stands, you might as well disassemble it and see what can be done with a circuit pen. Most of these keyboards have circuitry on sheets that sit between the layers of the keyboard. A circuit pen could be used to repair the offending trace.