Hi virus317,
First, please install the latest version of Bandicam.
And then, please refer to the following page and increase the output volume of the default sound device and the application sound. (Step 2-2)
https://www.bandicam.com/faqs/no_sound_ ... x_problem/
If you still have the same issue, please attach screenshots of Bandicam Recording settings window and Windows Sound settings window.
Thank you.