I have been having the same issue with exporting to mp4. It looks like some of you were recording the audio and then inserting that into the slide show. (I have read about doing that but have not tried it).

However, I was recording the audio directly into pptx2016 and not recording it as a separate file. The reason for this is that I want to be able to change slides out as needed and recording it in pptx means the audio is attached to that slide. This beats having to record the entire presentation again.

The weird part is that this worked fine 3 weeks ago.

I know that I can always record the presentation through gotowebinar or freeconferencecall, but then I lose the ability to edit single slides.

Any suggestions?