Thanks for reaching out to us, secampbe.

I want to ensure that you can generate the updated email address when invoicing a customer in QuickBooks Online (QBO). Let's perform troubleshooting steps to sort it out. It's possible that QuickBooks may behave unexpectedly due to data issues in your browser. To verify this, try using an incognito or private browser. To open an incognito window, you can use the following keyboard shortcuts:

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

If you continue to experience the same result, I suggest using other supported browsers. This will help us identify if the issue is specific to your current browser. 

Just in case you want to personalize your sales forms in QBO, feel free to visit this article for reference: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you need further assistance regarding this matter, don't hesitate to leave a reply below. I'm always here to lend a hand.