Triggering Purchase on abandon cart

Hi

Recently if someone adds a product to the basket then proceeds to checkout, enters their details and continues to click through to pay via paypal (only accepting payment via paypal) then close the page, not fulfilling payment, mailchimp triggers this as a purchase and doesn’t add the contact to the abandon cart campaign. Instead when I had automatic notifications it would send an email saying we have your order.

Any ideas on how to rectify this?