Hello Julio,
Are you using the slide preview feature when testing your object? Also, have you tried publishing the slide to see if this helps allow the Youtube video to load properly? I did a quick test on my end and made the following observations:
- An embedded Youtube video does not load properly when the slide is only previewed
- An embedded Youtube video loads and shows the thumbnail when the slide is published, and the published output is viewed in a supported browser
Attached is the file that I used for testing. If the behavior that you are reporting is present in both the preview of the slide and the published output, feel free to reach out to our support team here for further assistance.
