If you are a merchant using PayPal as your payment processor for your Zen cart e-commerce shop and your customer is having trouble making successful transactions, there are a few things that you can check.

First, let's take a look at the steps that a customer goes through during checkout:

Step 1 is where customer specifies the shipping address.

Step 2 is where customer specifies the billing address.

This can be different from the shipping address.

However, this address needs to be a valid address (not some randomly made up address). PayPal performs a validity check between the city, state, and zip code. And if address does not pass validation, you may receive the error "The address information you entered does not appear to be valid or cannot be matched"

In addition, if the customer is using a credit card, then it must be address in which the customer receives his/her credit card bills.

Step 3 is where the customer can confirm the information and make changes to it.

The customer is directed to a PayPal hosted page for credit card entry.

On this PayPal hosted page, make sure the address shown is again the same address as the billing address on the credit card used.

If you are a merchant testing your own store, note that you can not use a credit/debit card that is associated in your PayPal account under "Profiles -> Edit Credit Debit Cards". Use a different card that PayPal does not know about.