You posted this question to the Adobe Story forum. I'm going to move the thread to the Premiere Pro forum, where it will be seen by a large number of Premiere Pro experts who can help you. After I've moved the thread, I'll check back in and see if I can help get you an answer myself.
With the trial version, there is zero support for anything MPEG, but that should not be an issue here, unless you are trying for something like H.264.
I would choose an Export setting of MOV with the Animation format/CODEC. Those work very well, X-platform. Do NOT try for MP4/H.264, as the trial cannot handle that, or at best, not well.
What are your Export settings? That is very likely the issue.
PS - did not even know that there was an Adobe Story forum, so I learned something new today. Thanks Todd.
Here's the section of the Premiere Pro CS5 Help document that gives instruction for exporting a sequence:
Here's a video tutorial that covers the same material, but perhaps in a more friendly manner:
As suggested, I'd try something like a QuickTime movie with the Animation codec first, just to make sure that the basics work. (The Animation codec makes big files, but it's also a pretty standard way to make losslessly compressed intermediate movies, so it is a good choice for this little test.)
If one of the steps fails for you, tell us exactly what you're doing and exactly how it fails (complete with the exact text of any error messages).
Just a gut feeling - it was MP4, but hope that I am wrong, and your steps will point the OP firmly on the path to success.
Hopefully, we'll know soon.
At what point are you experiencing issues? Are you able to find the export option but unable to find the correct settings or is it failing after you try to export? If you can help give me some more details, I'm sure I can help.