Title: Play a video automatically in a slide show - PowerPoint
Headings: Play a video automatically in a slide show
Play a video automatically in a slide show
Play a video automatically when a slide appears in Slide Show
Another option: Play in Click Sequence

Content: If your slide doesn’t have a video in it yet, you can add one. Go to Add and play a video in a presentation for more information. Important: Certain older video file formats may not compress or export properly in Office on a Windows RT PC. Instead, use modern media formats such as H.264 and Advanced Audio Coding (AAC), which PowerPoint 2013 RT supports. Want to know what version of Office you’re using? Another option: Play in Click Sequence
Beginning with PowerPoint 2016, one more video playback option is available: Play in Click Sequence. With that option set, when you click anywhere on the slide to advance to the next step (or when you press the Spacebar, Right arrow key, or other key that advances to the next step), the video plays.