This means that the shipping address submitted to Printful does not match the address submitted to PayPal when the end customer went through their checkout process. PayPal Seller Protection is generally what causes this error to occur.
If your transaction is failing due to this error, you will need to find the transaction within PayPal, then verify that the entirety of the address (street, city, state, zipcode, etc) matches the address on Printful's end. If the problem persists, we recommend using your Printful Wallet to process the transaction.
Another option would be for you to disable Seller Protection within your PayPal account. This is not recommended, as it is a security measure which protects you as well as your end customers.