Twenty Seventeen Video Header

I need help with the video header in the twenty seventeen theme. I prefer to upload a video rather than use a link. However, the issue I am having is that upon uploading the video—the preview will show in the customizer but it does not appear in the header, only the original image does. I have tried different resolutions, different sizes (all under the 8mb limit), different time frames and even a different theme, but the same issue happens. I have also flushed the cache from WP dashboard and browser multiple times to no effect.

The forums that I have found speak specifically to this issue being due to mobile view, but I am working on an desktop so it does not apply.

Any help you can give would be appreciated, thank you!