Thanks for coming back here, @bexmg.

I want to make sure the settings in your QBO account is saved. Accessing the account on the regular browser will allow the cache to save site settings or memorize account history. 

If you are accessing your account this way, but can't save the changes to the invoice save options, make sure there aren't any third-party apps that will prevent QuickBooks from saving cache.

If you're still getting the same problem, I recommend contacting our Support again. This way our representatives can report this to our engineers for thorough review. Here's how to contact us:

1. Go to the Help menu in QuickBooks, then choose the Search tab.
2. At the bottom click on Contact us.
   
3. Enter the keyword Account Management and Billing in the What can we help you with? box.
   
4. On the next screen, scroll down to How would you like to connect with us section.
5. Choose Chat with us to initiate a discussion with a live agent.
   
6. Enter you account contact information then press Get a chat.
   
7. When using this option, make sure to enable pop-up windows. The chat box will appear at the bottom right section of your monitor, and an agent will be with you shortly after. See this:

Please drop by again if you have any other concerns besides this invoice question. I'll be right here to help you anytime. Have a good one!