I have the same problem and wasting days trying to solve it.
I am using prostore wordpress theme. I am setting up the ecommerce with woocommerce plugin.
When I place the order, thank you page does not load and I get the following error message
{"result":"success","redirect":"https:\/\/www.paypal.com\/cgi-bin\/webscr?cmd=_cart&business=MyPayPalAccount@Mail.com.....
can u pls help?
thanks