Some Chromebook users may see a black screen and hear audio playing when a video should be displayed. This issue affects Chromebooks that use an Intel Celeron 800 series processor.
Wait for the audio to finish and the activity will then show and be playable. A future release will include a rewritten video playback mechanism that will allow video playback.
This issue is fixed in the new Imagine Language & Literacy app, which was released on August 7, 2017.