Popup Pro not responsive anymore

Hello Support.

My website, http://www.secretauthors.com, uses Popup Pro for a custom login and registration and I integrated another plugin inside the popup box, PA Custom Login & Access when the user clicks "login" or "register". It used to show a beautiful popup before that adapts on whatever display size the user is using.

This responsive feature suddenly stopped working and when users try to login on their mobile device, the popup box is only visible in half. How can we fix this?

I tried to simulate the issue on Firefox and reduced the size of the browser and I can send a photo of the issue if you want.