Solution in 3 steps:
Bandicam sounds/audio, not recording is the most common problem its users faced. i will show you how you can fix this problem within 1 min.
Open the Bandi cam app on your laptop or computer. (Show in pic 1)
Click the Video menu shown in the below picture.
Click the Audio setting right side corner. As Shown below picture.
In step 4 click on each section of (Disabled) shown in the above picture and select the “Microphone”. E-g: Shown in the below picture.
In step five you will see the audio recording enable and show the wave of the sound in the bar.
This is the easiest method I have shown you in just a few steps. Hope it will help you out. For more info, you need to comment below.