My duplicate invoice function does not work.

Thanks for joining the Community, @ddonaldson.

Let me assist you with how to fix it. Your browser may be having cache issues. This is why QuickBooks Online (QBO) is unable to duplicate an invoice since cache files can impact processes and cause unusual behavior when held for a long time.

I suggest running QBO in a private browser to isolate this issue. Then follow one of these keyboard shortcuts for your browser:

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

If you're able to duplicate an invoice, you can go back to your regular browser and clear its cache. The cache is stored to speed up loading times and optimize QuickBooks Online performance.

Alternatively, you can log in to other supported browsers like Firefox or Chrome to see if you can duplicate invoices from there.

While giving it a try, I'll wait for your reply. You can always comment if you need more assistance. Stay safe and well.