To get subscribers to watch a video on a sales page, your email needs to create a strong reason for them to click away from their inbox and go to the page. You should talk about the biggest problem the video solves and tease a key piece of information they will only get by watching it. Instead of linking to the whole sales page, maybe link directly to the video player if you can, or use a big button that says "See the 2-Minute Explanation." The goal is to make the video sound so valuable that they cannot ignore it. Do you think offering a short summary of the video in the email helps more people click through to watch the whole thing?