Links for PayPal redirects are not absolute
Most probably a missing Entry Point for a domain in the site configuration -
https://www.domain.tld/ should be used here
Products cannot be added to shopping basket
The route enhancers have probably not been configured. If page type
shop.json: 1496773586 is not defined, AJAX requests cannot be routed.
If the shopping basket button still doesn't appear, you may have the static templates in the wrong order. Static templates must follow the order in the static template which defines content elements.