Blank page displaying -1

When I use this plugin on my new site and I click the paypal button either on the cart page or the top of the checkout page it redirects to a blank white page that just displays “-1”. This does not happen if I choose the option from the general list of gateways on the checkout page. Can you please tell me how to fix this? Thanks

https://wordpress.org/plugins/paypal-for-woocommerce/