Here's the Nokia 2690 Solution for not working mic problem. This solution below shows the complete connection tracks of the microphone that can be used for deeper microphone problem troubleshooting.
To fix or repair mic problem on Nokia 2690, you may first check the microphone module using a multimeter or replace it with a new one to securely confirm that the microphone is still working or not damaged.
If the Microphone is okay, clean the mic's terminal contact pads. Refer to the solution below and do some check and test procedures.