On Nokia X2-01 keypad matrix, the inner core and outer layer of each keys were highlighted in color, those color represent where and which group they being connected. The lower photo is the two keypad EMI filters which if damaged it will result a keypad malfunction on Nokia X2-01.
Here's some hints on how to fix Nokia X2-01 keypad not working problem:
1. Check the device firmware, try to re-flash or update.
2. If the device suffered wet damaged, clean the keypad matrix and the keypad membrane.
3. If there are only few keys that is not working, trace the connection between to the other keys...
4. If the connection seems okay, the last option is to check the Keypad filter IC's.
Try to rework it first, check the solder ball bumps for possible damaged..
5. Replace the keypad filter IC.
Nokia X2-01 Keypad Connection Tracks prepared by GsmAngel