Hi Brian! My name is ***** ***** it is my pleasure to assist you this evening.
Is there any chance that your card is tied to another existing PayPal account? Barring that, is there at least $1 available on your account to accommodate PayPal's temporary verification hold?
If neither of the above, is the website giving you any error message when validation of your card fails?
I'm glad you found the issue! If you're able to disassociate the card from your PayPal A/C, you should then be able to successfully register it to your account.
If we can be of any further assistance, please let us know.