Hi Ron,
Thank you so much for your reply. I was embedding a video from Vimeo. Good to know poster frames never work with embedded videos.
It's a pity though because I would like to avoid having to upload my videos, so keep the size of the entire course small. Is there a work-around?
Please find attached screenshots: I was replacing the first frame as shown in the first screenshot, the second one shows the preview (with the picture being half cut off unintentionally) and the last one the actual course (showing the first frame of the video instead of the assigned picture).
Thank you, Anja