I once had my prepaid debit card linked to my account with no issues. After a threat was made to hack into my account, I removed all forms of payment. Now that I have secured identities and accounts, I have linked my cards once again (and have set as preferred payment method). My account says that the card is linked, but when I try to withdrawal funds, I cannot get passed the "link a debit card" stage. It'll make me enter in the card information, confirm that the card is linked, but won't go any further. Effectively preventing me from withdrawing my funds. Why could this be? As I said, I once used this same card months prior to withdrawal funds with no issues whatsoever.
As this is a public forum, it's not possible to look at user info - you may want to contact customer service for assistance. What we do know is that if you have a card linked and later remove it, in most cases you cannot re-link the card again without assistance from customer service. This is actually a fraud protection action put in place to protect you, the card owner. For example if there was no security in place, if someone had access to your financial info, they could simply add it to their account.