The latest rekease of symVide5 2.0.5 requires a 2 step upgrade process due to changes in  the template structure as well as the core code. 

Upgrade Notes

Additional stacks created for All Formats (Web M and OGG , H.264) or just H.264 media have undergone some changes

Grab the latest templates for symVideo5 now

After installation and successful restart , to ensure that full window function will work on your existing pages you will need to swap out the old template (h.264 or Allformats) with the new one in your opened Stacks Page and then republish

Make sure to relink your video files to the Add Media Stack.

If you are experiencing problems , try publishing with a test page first of all before contacting support as this will verify that you are using the old template if you cannot get the full window effect in Chrome or Firefox with native HTML5 media