Hi minhkhanggg -
I can certainly see where this would be a concerning situation, and I'm glad that you've reached out to us here on the Forums for an answer. A preapproved payment is actually where you've set up an agreement with a merchant, that they can go back in and charge your PayPal account under certain circumstances, without you needing to log into your actual PayPal account. Many digital merchants use this process, so you can stay on their site and use their services while making payments through PayPal. You can manage these types of agreements here.
As far as them not receiving the payment, if it's showing as Complete on your end, then the money's been sent to them. Depending on a few factors it may potentially be held on their end, however they would most certainly have at a least received it. If they've any questions about that, I would recommend they reach out to PayPal directly, so we can discuss their account with them.
I hope that helps clear things up a bit.
- Andy
