Subject Field Popping Up

I have custom code for a form block on my website that allows customers to "inquire" instead of "add to cart" on products in stock. The form block now gives an error message stating there needs to be a subject in the subject field, but there is not actually a subject field. I want to know how to remove the subject field so customers can inquire about the item. 

Please post the URL for a page on your site where we can see your issue.

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.

We can then take a look at your issue.

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

https://www.shedhorn.com/shop/p/sig-sauer-p320-10-10mm-pistol

Here's one page with the Inquiry button that is malfunctioning. All firearms on our website have the same Inquiry button.