How To Shift Scrolling From Background To The Size Chart Pop Up (2023)

I have a popup for size charts enabled through the RT Size Chart Builder. It works great, but something is keeping the scrolling fixed. When you are on mobile and the pop-up is open, all you do is scroll the background, not the pop-up. The pop-up clearly needs to be scrolled to see the rest of the “how to measure” tab content. How might I fix this? It works fine in the preview inside the RT Size Chart Builder app. My site is ByGraceAloneDesignCo.com. No password and I’m using the Dawn theme version 9.0.0. Here is the product page I have it enabled on: https://bygracealonedesignco.com/products/cat-mama-proverbs-12-10-v-neck