My customers are un able to view there invoices. It just says ‘invoice unavailable’

Hello there, userjoefarrier22.

Thank you for reaching out to the community and letting us know about the unexpected behavior they encountered in QuickBooks.  

Did your customers try to view their invoices using an iOS device or Safari? If that's the case, we have an open investigation about seeing invoices that are unavailable using an iOS device. We received a few reports recently, and I would encourage you to contact our Care Support team to add you to the list of affected users. As soon as the permanent fix has been released, we will let you know via email.

On the other hand, if they're using Android or Windows to open the invoice, I can help you fix it by performing a few browser troubleshooting steps. You can let your customers access their accounts through a private browser. It's a great way of isolating the issue since it doesn’t store data in the cache. 

Here are the following keyboard shortcuts: 

• Google Chrome: Ctrl + Shift + N
• Microsoft Edge: Ctrl + Shift + P
• Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

From there, let them view the invoice again and verify if it's showing. If it works, go back to their regular browser and clear its cache. This deletes the stored cache files and gets a clean slate in the browser. They can also use other supported browsers. 

You might also want to check this article that provides detailed information on how to give your invoice a unique look: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Thank you for your patience while we work for a fix. If you have other questions or concerns, please let me know in the comment below. I'll be more than happy to help.