To make sure the payment can link to your account, I recommend making sure that your PayPal email address is confirmed. If it's already confirmed, you'll want to find out what the exact error message is that they're receiving. There's a chance that the error is something on their side. For further assistance, you can reach Customer Support by clicking 'Contact' at the bottom of any PayPal website. Support is also available through Facebook private message or Twitter direct message.
I hope this helps!
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