If you are having trouble getting your PayPal payment to go through, it may be because you might have an un-confirmed address. Here is some additional info that might be helpful.
What is a confirmed address?

A confirmed address is an address that has been reviewed by PayPal and found to be safe based on information related to the address. For example, a credit card billing address is confirmed because PayPal can check that the address is the same as the address on file at the credit card company. PayPal provides confirmed addresses to help sellers make informed decisions when shipping goods. As a general rule all accounts have at least one confirmed address and using an account will help increase the number of available confirmed addresses in the account.
 
How do I confirm my address?

To confirm your address, you will first need to add a credit card to your PayPal account. If your credit card company supports the Address Verification System, PayPal will check that the address you provided for your account matches the billing address that your credit card company has on file. You may be required to complete the Expanded Use enrollment process, to activate your credit card. Your address may be confirmed after the Expanded Use enrollment process has been successfully completed.

Why do some sellers require buyers that provide a confirmed address?

A confirmed address provides sellers with confidence in shipping to the address provided with a payment. A confirmed address is an address that has been reviewed by PayPal and found to be safer than addresses that do not have similar characteristics. For example, a credit card billing address will be confirmed because it is a safer address than most other addresses. PayPal provides confirmed address information to help sellers make informed decisions when shipping goods. Non-confirmed addresses do not qualify for the PayPal Seller Protection Policy.

If you are unable to confirm your address with PayPal, you can still pay for your purchase with Check or Money Order.