One key died suddenly. Suggestions?

Last weekend my mechanic did my FSR, and had the battery disconnected for a while. Car's running great except for one thing--the buttons on one of my keys aren't working.



I tried the "hold down one button, click the other three times" fix, and that didn't seem to work.



Any other suggestions? The key is pretty old but it died pretty suddenly, and since it died immediately after this electrical service, I'm thinking/hoping it's the programming rather than the key/battery.



Thanks in advance.