Hello borate,
The version I am using is 10.12.
Here is a link to an MP4 file that I loaded and rotated. I have cleared cache, rebooted, reinstalled as still the Export Video option is greyed out and not usable.
https://drive.google.com/file/d/1YKrSf3kQFZN5akwM7unkq387a-rEnAqo/view?usp=sharing
I appreciate your help!
Moola