Hello,
Using magento 2.4, full dns transfer, page cache rules set as recommended in the docs here for magento.
Whenever CF cache is enabled, the add to cart button gets disabled on my site, it turns grey.
Has anyone else ever run into this issue?
Greetings,
Thank you for asking.
Are you using a Paid plan?
May I ask if it’s the link from below, or some other? 
The HTML state of the button is disabled, or CSS changes, or JavaScript doesn’t work, or something other?
Is the “cart button” located as “flying cart” or rather somewhere fixed on your website like “menu”, etc.?
What’s the domain name?
Any other caching system running at the origin host/server?
Are they the only one or there are some more Page Rules as well?