What errors do you get in the Developer Console?
Chances are that you’ve hit a CORS issue and/or you are linking to http content from https. There’s quite a few threads in the forum regarding, hopefully they will help: app.assets.loadFromUrl() is blocked by CORS policy
If the application and video content is all hosted on the same server and domain, that will work. Otherwise you will have to setup CORS headers on the server serving the content.