I found this thread because I’m having similar issues. My project (CS6) isn’t encoding. It just sits there at 0%. I read a whole bunch of solutions: reinstalled, updated, tried exporting with match sequence settings, etc.
In the end, I noticed that one clip’s audio was on a mismatched audio track. The clip sat in video 2 while the audio sat in audio 3. I had no idea that this mattered, but when I moved it, it worked. I’m sitting here, happily watching my sequence export.
Hope this helps someone.