Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Your new Paypal card and number, will not work with old facilities/links/etc. that are configured to the old card/number. This should be fairly obvious.
But I should ask: where, and in what ways, do the new card and new number, not work?
The new card and number (I have to ask:) Did they involve a new account, a new Paypal name, etc. ?
If you were trying to buy using Paypal from e.g. Amazon.com, you might have to register your new means-of-payment with your Amazon.com account, before Amazon.com would accept it as a means of payment. Was that the situation, and what you are asking about?
To attach a new card to your paypal account, log into your paypal account, and register it there. Nothing simpler, once you know where to look.
(If you need specifics, let me know.)