I have the same issue -- but I cannot connect to Paypal from within the Admin -- if I am not logged in, then the Add To Cart does absolutely nothing. This is happening on: http://lifesongcollection.com/.
This seems just a little more similar than the post I inquired on earlier today, so I'm trying to lock-in on the issue in 2 similar support requests: https://wordpress.org/support/topic/guest-can-not-add-to-cart?replies=9
Please advise... increasing number of customers turning away frustrated!
Steve C.
3Cstudio