Store Items are always unchecked

Hi, 

I have this extreme weird behaviour with Squarespace 7.1. I have NO code in the website.  Only standard stuff.  I am redoing my website and store.  When I mount the Buy button the store... the store lands on an empty page. See video.  I have not idea what is happening. I am not a programmer... I am a photographer who uses a website. 

Anybody can help? 

Please post the URL for a page on your site where we can see your issue. For us to see the URL you need to include the link in the content of your post. The URL field the forum software provides is not shown to us.

A link to the backend of the your site won’t work for us, i.e. a URL that contains /config/.

Please set up a site-wide password, if your site is not public and you've not already done so.

Post the password here.

Adding a site-wide password does not allow anyone to alter your site. It only allows those with the password to see your site.

Please read the site-wide password and how to share a link documentation to understand how they work.

You may find How to post a forum question post useful.

We can then take a look at your issue.