AMAZON CLOUD - WHEN WILL IT WORK

HI All,
So, yeah, the whole idea of putting my stuff in the cloud and having it work EVERYWHERE sounds awesome!
I signed up for the Amazon Drive, uploaded my files, and then tested it out: IT DOES NOT WORK
WHY does it NOT WORK? My files are all in .mp4 format?
They are ALL in the PLEX CLOUD SYNC folder.
Yes, my Plex & Amazon account are linked...
SO - WHY DOES IT NOT WORK? WHY will Amazon Drive only play a video file that's less than "20 minutes long"?
And what's up with needing 'an invite' for a Beta program?
*I've got 3 months to cancel or be charged the $50/$60 per year from Amazon Drive - and I'd like it to work NOW
If anyone's got any ideas, thanks in advance.
I have the PLEX PASS and it's pretty awesome - unless my house loses power and my pc turns off.