Insert the video into the presentation

Why this matters: The presentation only points to a video file on your own computer. That file doesn't travel with the presentation, so the video slide will be blank at the venue.

PowerPoint for Windows

1. Delete the linked video from the slide.
2. Choose Insert → Video → This Device… and pick the video file.
3. Make sure you choose Insert (not Link to File) in the Insert button's menu.
4. Save and upload the presentation again.

PowerPoint for Mac

1. Delete the linked video from the slide.
2. Choose Insert → Video → Movie from File… and pick the video file.
3. Leave Link to File unticked.
4. Save and upload the presentation again.

If that doesn't work: If the presentation gets too large, you can instead upload the video as a separate .mp4 file with the presentation and tell the organiser which slide it belongs to.

The checks run in your browser before the upload and again on the server. The server's result counts, and you see it on your upload page and in the confirmation email. See also the technical guidelines for your presentation.