@Phoenixesper1 Unfortunately, this is a compatibility problem between certain legacy macOSX versions (particularly 10.11) and the FFMPEG plugin which is used to export movies and images.
A Pencil2D developer with macOS experience was working on a potential test build to improve this for Pencil2D 0.6.5 but there’s currently no copy available and since we’re all volunteers on the project they can’t currently spare enough time to commit to this fix.
However meanwhile we get a hold of them, please consider the following:
In the forum a user with a similar issue provided a guide to compile FFMPEG from source to help legacy macOSX users with this problem: Export not working in legacy OS X version apparently their own FFMPEG compiled file worked as expected.
Consider compiling the ffmpeg version required for your OS and then replace it in your .APP folder for Pencil2D. The FFMPEG file is found in the folder structure:
Pencil2D.app
-- contents
--- MacOS
---- plugins
----- ffmpeg
You could also try to use the same user’s pre-compiled ffmpeg build made for 10.7 https://www.dropbox.com/s/jncl1a9dd8tt7rp/ffmpeg?dl=0, however I can’t assure that it will work for your particular macOSX version.
Also be wary that it is a third party file, not something made by the Pencil2D maintainers.
I’ll update you once I have more info on a proper fix for upcoming updates.