Currently, you have popup HTML code in your Theme Settings and you should be able just to replace image path with a new one https://gyazo.com/8a0ae2ac16d1bc2da44e6abb53b92885
We suggest you create a new HTML Block in Dashboard using WPBakery page builder that is a much easier way and doesn’t require coding skills. Then, just put this block’s shortcode to the promo popup field in Theme Settings.
Note that we didn’t change anything in our updates regarding promo popup functionality.