The Slice tool generates both an HTML file and an associated folder of images.
The code in the HTML file contains the slice tool coordinates, the <img> tags pointing to the images and the hyperlinks behind each image.
In your Loom video, you have only emailed the banner.html file.
When you open banner.html, the images display as missing files because the folder containing the images does not exist where the <img> code is expecting to find them.
You must email both the HTML file and the folder of images. They (HTML file and folder of images) must then be saved in the same folder on the local device so that the relative path links in the HTML file work.
Then the banner will work OK in the web page.