Out of curiosity, did you check out What is PayPal Preapproval? How do I use Paypal? ? It says:
If you do not select a secondary funding source before you approve, your payment will fail.
Secondary Funding Source
Funcom requires players to have a secondary or backup funding source even if there is enough credit on the PayPal account to cover the balance. Players will need to register and select a Secondary Funding Source.