the Name & Number addon on mobile is not working fine the toggle to show the list of t-shirts.
Also, by default the list is hidden making it not usable for the user, who has to click on the fpd-mainbar to see that he can customize the t-shirt.
It's necessary to solve it so we don't get lost customizations.
Here's the screenshot on mobile.
Please open a support ticket so we can have a closer look at your issue.