Issue with Flex box on Safari mobile

Hi I am having an issue in Mobile when using Safari it is not respecting the positing of a pop-up form, it ends cropping it at the top. This is fine in Chrome Desktop and Mobile, I tried to check and use the designer in Safari as well but the issue does not show when working on the site or previewing. Only on iPhones and Safari. See screenshot attached.

Site preview, need to click on “sign up” to see the pop-up

Here is my site Read-Only: LINK
(how to share your site Read-Only link)