Error compiling movie. Unknown Error is very difficult to solve.
It can be anything from a faulty clip ,effect, audio clip etc.
Just a few basic questions:
Which OS are you using?
Which export settings gave the error?
What kind of media is used in the timeline?
What is the final destination of your project? Flash drive, tv, ....?
Also make sure that you don't have a Stop Marker at the end of your movie and that there are no video blank spots on your video timeline.
To supplement, please check out the Adobe document on Premiere Elements and "compiling errors"
We will be watching for your progress as your schedule permits.
All of the export settings have given the error message including online video.
The final destination is the hard drive of the computer I am working on.
OSX comes in a number of different flavors, including El Capitan and Yosemite. And El Capitan has been known to have a number of issues.
But that said, have you considered my suggestion above?
Stop Markers at the end of a movie and video gaps within the movie are the chief causes of export failures.