I was having a real problem with inserting video directly from my webcam (Microsoft HD 300) The recording would start OK and then the audio would quit after about 25 seconds. I was surprised because I have been using the webcam with no problem for other applications and as a mike for adding audio alone to Storyline.
Somewhere in these pages it was suggested to update the webcam driver, and that fixed it! I probably never had a driver in the first place as the webcam worked so well when I just plugged it in. Drivers for all Microsoft webcams are on their website.