I have exactly the same problem with my credit card security code.

I have re-entered the card details 3 times so far.

I have communicated with eBay by email and telephone and WEB chat and the people I talk to DON'T HAVE A CLUE on how to fix the problem, so my account has been suspended.

eBay are the cause of the problem, yet they make me suffer by causing me to spend hours; over 14 days; to try to get a solution, but won't or don't know how to help me.

Customer communication is dreadful, if no non existent and amazingly when I log into the "One-time payment link" I get told I don't owe eBay any money at all.  Go figure!