HELP - Pay with PayPal - goes to incorrect screen

[Frameskin]

Hi there. I am running PS v 1.6.1.2 and in the last 10 days or so customers have been reporting that the Paypal module goes to a blank screen when someone tries to buy. They can go through products, select one, put it in the cart, login, go to the payment screen, select "Pay with PayPal" and then get a blank screen. 

 

Any ideas as to why this is happening? Nothing has changed regarding our PayPal credentials. The rest of the site is functional... except the important bit – getting paid for orders

 

Any advice would be appreciated

Alan

Edited October 9, 2017 by Frameskin (see edit history)