Why does the Buy Button disappear on my site after navigating subsites?

[nopress]

Hello everyone, I connected Cargo website with Buy Button. Everything is working fine, orders are slowly rolling in. The problem appears if a user clicks on a subsite and then returns to the main site where button is located, button dissapears. The button appears again if you refresh the site.

This is obviously very annoying, because some customers cannot purchase the items because the button is dissapearing. How to solve this? Website url is www.no-press.eu

Thanks in advance!