Trouble connecting to API via curl.

Having an issue with this plugin, I get this error when I activate it and visit the settings:

Whoops, your server is having trouble connecting to the WPMU DEV API! If this problem continues, please contact your host and ask them to "make sure php and any firewall is configured to allow an HTTP GET call via curl or fsockopen to https://premium.wpmudev.org/video-api-register.php.

How can I resolve this?