Cursor/Select button doesn’t work

So I want to fix my mother-in-law’s Kindle 3. I have a Kindle 3 that I’ve successfully replaced the screen, so I’ve taken apart one of these devices before. The problem with her device appears to be the entire cursor/select button. The button itself feels right when attempting to use it, i.e., it clicks, etc. There is just no response. The rest of the keyboard works fine. So my question: is it a simple replacement of the cursor/select button or something else? The mother board perhaps?

Thanks,

Jim