Required if Youtube is used (not required if you just want to use Youtube single videos and you will be providing video thumbnail, title and description yourself). Register here: https://console.developers.google.com and create new project, enable YouTube Data API, go to Credentials, create Browser key and enter API key.
Required if Vimeo is used (not required if you just want to use Vimeo single videos and you will be providing video thumbnail, title and description yourself). Register here: https://developer.vimeo.com/apps/new and create new application, and from Authentication tab get: Client Identifier, Client Secrets and Access Token.
Error with File Permissions. If you want to use Vimeo API, Please set write permission (755) to your wp-content/plugins/apmvp folders to make sure Player can save Vimeo access data.
CURL not enabled. If you want to use Vimeo API, Please enable CURL.