On what computer operating system are you running your Premiere Elements 11?
I have never gotten involved with the Video Press plugin on a WordPress site.
Assuming the following is what you are trying to work with
What are the properties of your .mp4 Premiere Elements 11 file that I assume you have saved to the computer hard drive
for upload to the web site from there.
Have you seen the following and gone through all the recommended steps for the video upload?
Please review and consider.