Client is not able to pay with credit card on their invoice. The online payments is set to "on" and it is giving her an error message when she goes to pay with her mc

Hi there, 

Welcome to the Community. It's important you're able to receive payments from your client. Rest assured, I'll be glad to guide you in the right direction. 

To get started, I recommend having the client clear cache and cookies on their browser in case they're having browser-relate issues. Clearing cache and cookies is a great way to clean your browser allowing it to work more efficiently. Here's an article that shows you how to do that: How to clear cache and cookies. Give this a try and let me know how you make out.

I look forward to hearing back from you in the comments below. I'll be here.