If you're still within the first 24 hours since the payment was listed in Splitwise, the payment confirmation may not have reached Splitwise yet. We do not control when PayPal sends up payment confirmations and it can take up to a day to get to us.
It's also possible for someone to start sending you a payment via PayPal, but then to quit halfway through and not actually transfer the money. These payments show up on Splitwise as "pending", since they are waiting for the payer to complete the transaction and send the funds.
If you're sure that your friend has actually sent money through PayPal, then it's also possible it went to the wrong address. By default, PayPal payments are sent to the email address associated with your Splitwise account. If you don't already have a PayPal account for that address, then you should receive an email at that address with instructions on how to claim your payment. To keep this from happening you can add your Splitwise email address to your PayPal account- you can add up to 8.
If you're still not sure what's up, then feel free to email us at firstname.lastname@example.org. Unfortunately, we do not have any visibility into your PayPal transactions (PayPal is a separate company, and does not give us access to any of that information), but we'll help as best we can.