Did you register both your name and address with the card issuer?
Prepaid cards are a challenge to use thru PayPal:
Per PayPal's own Help FAQs, they state the following: You can't link a gift card, prepaid card, or one-time-use card to your PayPal account. From our experience the exceptions are, PayPal Products or Green Dot Money Packs or a Prepaid Card that allows you to register both your name and billing address.
Suggest not trying to link a prepaid card to your PayPal account unless the card is a PayPal Product or a Green Dot Money Pack or you have contacted the prepaid card issuer and registered both your name and billing address with the card. Note, there’s still a risk that the registered prepaid card may not be accepted if the name does not match the PayPal account name or the billing address is incomplete.
With many prepaid cards, there's no owner name or billing address information nor is there a way to include that information on the card. There’s only the card number and an amount. PayPal can see the amount but, their security checks cannot confirm the card owner as there’s no name or address info. When that happens, you are asked to use another funding source.
If you try link the card, you may have some dollar amount removed however, the linking process will fail. In other cases, you can link the card and may even have a small amount deducted from the card while trying to confirm it but again, you may not be able to use it for a purchase. As for how you go about getting that dollar amount returned, you may need to contact customer support for assistance or the card issuer or both.
