I think these was an error in the defavid.php functionalities
It have several guidance to look at
First , Make sure video can direct access to the real video file . Like https://www.example.com/test.mp4
The file that host on Server which have php or api functionality like Google Drive , Vimeo or Youtube are at risk.
Second , Check Your Server Configuration ,
Try install on WAMP Server or XAMPP Server Configuration which is the common default and test that it works with your current wordpress environment or not.
Advance
Third , Try Turn WP DEBUG On , Make sure there is no conflict or error. The common error is
WP Header Already Sent
The error was looking like this :
Cannot modify headers , header already sent … at line ..
If it was like that , There are serveral ways to fix WP header already sent from disabled plugin , edit the code of other plugin and stuff but the most easiest way is to download our WP header already sent fix patches :
https://www.juthawong.com/downloads/wordpress-header-already-sent-fix-plugin-for-free-and-paid
and also there is some rare case .
which you may need to contact our service partner team :
[email protected]
Thanks