Hey there, and thank you for reaching out; I’m familiar with a similar issue due to a Windows N Update.
To fix it, update the Windows media feature pack for Windows N edition
To find your version of Windows, right-click on the start button on the Windows taskbar and select “System.”
Your computer’s version will be listed there.
Once this is updated, you should be able to export the video as an Mpeg.
Let us know if that works for you.
MC