@mo_282971
When you refund via PayPal the funds go back to the original payment source. For most buyers this means the credit will show up on their credit card. They can check online but need to understand that refunds to a credit card can take several days or more.
If they paid with a bank transfer (still an instant payment if they have a credit card on file) it goes back to the bank which also takes time (less than a cc). The only time the refund will show up in their PayPal account balance is if original payment was made from a balance in their PayPal account.
I have to ask, why are you cancelling orders? This is something that should be a fairly rare event.
Paranoia strikes deep
Into your life it will creep