Some browsers don't allow playback of video unless manually initiated. While this behavior makes sense when used as a traditional web browser on a laptop or tablet, it interferes with Blocks need to play video unattended. If you run into issues with video not playing, you may want to check/change the settings described below.
To allow Blocks to auto-play video and audio in Chrome, do as follows:
When using Chrome on PIXILAB Player, this setting is handled automatically.
In Safari 11 and later you need to change the following setting in Preferences to make videos play automatically.