PayPal works a little differently than regular payment processors.
PayPal does not offer full integration, so it works as follows:
The donor completes the donation form on your HiRaiser campaign/donate page.
The HiRaiser system records a pledge, and sends the donor to PayPal to complete the transaction.
You receive a notification email of a PayPal pledge (transaction pending).
The Donor makes the payment on PayPal, and is redirected back to your website.
PayPal sends a payment confirmation to HiRaiser. HiRaiser marks it as paid, and you receive a second notification email confirming the payment.
If the donor does not complete the PayPal payment, you will be left with a pledge that has to be accounted for. If the donor immediately submits a successful donation (via PayPal or credit card), HiRaiser should automatically cancel the open pledge. If they do not do so, or they submit it at a later time, a decision needs to be made regarding how to handle the open pledge – either cancel it if they end up paying using a different method, or if they do not follow up to inquire if and how the donor would like to pay their pledge.