If you are sure that the microphone is working, yet you can't record sound with FonePaw Screen Recorder, here are what you should do.
Make sure your computer is the default audio device
FonePaw Screen Recorder uses the default audio devices on your computer for recording and playing sounds. So first of all, you should check your sound settings to see if the computer is using the default playback and recording devices.
Right click on the speaker icon on the taskbar and select Playback devices, which will open the Sound settings of your computer.
Check Playback and Recording tab to see if the default device is selected. For example, in the screenshot below, the computer is using the default device - Conexant SmartAudio HD for playback and recording.
Make sure the default audio device can be used by different applications
It is possible that another application is occupying the default audio device. You can reconfigure a sound setting item to allow FonePaw Screen Recorder to use the audio device.
Open Sound settings. Click Recording and select the default device. Click Properties.
Click the Advanced tab. Tick Allow applications to take exclusive control of this device. Click OK.
Update Audio Driver
Open Device Manager. Select your audio driver. Right click on Speaker and click Update Driver Software. Then select Microphone and update the drive.
If the problem persists, please contact FonePaw Support via firstname.lastname@example.org.