Why am I unable to pay?

You can't. It seems to be a system problem. Call Rover Support at [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team] to complete your transaction.

It may make sense to verify your name, address and phone match exactly what appears on your credit-card statement. AVS is "address verification system." It can be touchy and flag transactions over minor differences. Most merchants catch this error and present a user-friendly response to the customer.

It could also be something Rover is doing. For example, misconfiguration of the interface with AVS. Or, encoding characters incorrectly. It could be something only they can fix. But, typically that error means the bank is supplying incorrect info, or you are.