When exporting a project from Camtasia for Mac 2 or 3 in a specific manner the resulting file shows in Finder as 0 KB:
Camtasia 2: Share > Advanced Export > Export to MP4 (not Export to Main Concept .mp4)
Camtasia 3: Share > Local File...>Export to MP4 (not Export to Main Concept .mp4)
There are two reasons this behavior can occur.
In the Advanced Export Options you are choosing a Custom Audio Data Rate and choosing something below 30 kbits/sec or above 255 kbits/sec.
Set the Data Rate for the audio between 30 - 255 kbits/sec, or choose the Automatic setting. *We recommend Automatic.
There is a bug in Camtasia for Mac than will cause certain project's to display this behavior, even when the above solution is met.
Change the video profile in the Advanced Export Options to any of the options with "AutoLevel":