Quickbooks changed all existing invoices in the app from a unit rate to an hourly rate, and changed what displays to the customer on the invoice. How do I fix this?

This happens because QuickBooks is transitioning all accounts from the Old Layout (Classic) to a New Layout (Modernized). During this rollout, the QuickBooks mobile app often defaults to the new layout rules, which convert standard unit rates into hourly metrics and change what your customers see.

You can temporarily switch back to the old layout using a desktop web browser. Once you change it on the web, the layout in the mobile app will automatically update to reflect the change and revert to normal.  

Please respond to this post if you have any additional concerns regarding QuickBooks.