Safari won't play Google Drive Videos

When I try to play videos posted to my Google Drive account Safari will not play these back. The video player shows up but just spins and spins without ever loading the video. All other web browsers I've tried (Firefox and Chrome) playback the videos just fine (on the same MacBook Pro over the same WiFi network). The videos also playback fine on a Windows 7 machine in Firefox and Chrome.

I'm running Safari 8.0.8 on a 2011 MacBook Pro running OS 10.10.5.