Hello, @christineRL.

I understand the impact of any delay in resolving this unexpected behavior when letting your customers view their invoices. Let me guide you on how your customers would see their invoice details.

Once your customers received their invoices, they'd initially see the total invoice amount. They have to click on the Review and Pay button to see the complete invoice details. 

They's be routed to a new tab where they'll see the option to view, download, and print their invoice.

On the other hand, you can let your customer try viewing their email you've received using a private browser or an incognito browser. This way we can isolate the prompt for a possible browser-related. Here are the shortcut keys you can use:

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

If they're able to successfully view their invoice, you'd want to let them clear the cache of their regular web browser. Also, you can use let them use other supported browsers.

Stay in touch if you have other questions or concerns about invoices. The Community is here to lend a hand. Thanks for joining and I wish you have a lovely day ahead.