Why is my keyboard not working but my trackpad works just fine?

For a while now Ive had issues with my keyboard becoming unresponsive randomly, even sometimes it works for seconds and the caps key will light up green as i press it. After seconds then it'll stop working, it went a while working after I reset the software and reset the computer completely, but then when the laptop died and I went to charge it... the keyboard stopped working again, the backlight still illuminates and the trackpad works fine. I'm not sure if a whole new keyboard needs to be installed or whether it could be someone as small as the flex cable. Please help.