We've had reports - mostly from schools using Chromebooks - that the videos won't play.
At least some of these reports appear to be due to firewall restrictions.
Workaround: Wait for 90 seconds so the fallback video can start.
If the workaround is not helping, please send a Help request which includes information about the equipment you are using and the network response data. This should help us rule out and perhaps pinpoint the cause.
Internal ticket: 224376610179969
Former internal ticket: 182055296736789
Dec. 14th 2016