PPV not completing transaction

I have installed PPV on the following page:


I have all of the paypal express settings populated. When I try to pay to see the PPV section, I am redirected to paypal as expected, log into my paypal account sucessfully, paypal correctly displays the price, and I select my payment method. When I then click the continue button in paypal, the screen puts up the paypal wait icon briefly and then returns me to the page on my site without enabling the PPV section.

I never receive a notice of payment being made from paypal so I must assume the transaction is failing but without any information on why.

Reloading the page on my site does not expose the PPV content.

There is no button on my page when paypal sends me back to it to confirm the price.

What is going wrong?