Reviw and pay not working on customer end of email.

I'm here to provide some steps to fix the issue regarding the inability to use the review and pay button for your invoices, Leigh.

Beforehand, did your customer encounter a specific error message while clicking the button, or it's just unresponsive?

One of the possible reasons why your customer is having issues with paying invoices can sometimes be caused by a stored cache and cookies in your browser.

That said, you can have your customer perform some troubleshooting steps to rectify this issue. They can start by accessing their email through a private/incognito window. The private window will not save any history, making it a good place to identify browser problems. 

Here are the shortcut keys:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Safari: press Command + Shift + N

If the private browsing session works, they can return to their regular browser and clear the cache to improve the program's performance. Otherwise, using other supported browsers can be a good alternative too.

Additionally, check out this article that outline how to customise the look of your invoices to match the branding of your company: Customise invoices, estimates, and sales receipts in QuickBooks Online.

You can always count on me if you need a hand processing payments in QBO. Just hit the Reply button, and I'll be right here to assist you.