*** I know this post is 4 months old, but just wanted to comment for future searchers with the same problem. ***
What Even said is (partly) true when you are encountering the issue where your video only ends up being 5-20 seconds long.
This plugin works by temporarily uploading the video to YOUR server and then it uploads it to YouTube. So, if your server is setup to only allow a max_execution_time of 30 seconds or an upload_max_filesize of only 2 megabytes, your upload will get cutoff before it finishes.
To fix this you must make a change in your PHP.ini file(s) to change these three variables:
"max_execution_time"
"post_max_size"
"upload_max_filesize"
Here are my setting for each:
max_execution_time = 1200 (This is in seconds, so 1200 seconds = 20 minutes)
post_max_size = 155m (This is in megabytes and should be slightly higher than upload_max_filesize)
upload_max_filesize = 150m (This is in megabytes and is essentially the max file size you can upload)
You might have to restart your server or, if possible, restart the Apache httpd service before these settings will take effect (I had to).