Hello there, @KD12.
I want to ensure you're able to edit the invoice template in your QuickBooks successfully. Let's get started!
Since you're still using the Trial version, let's uninstall and reinstall your QuickBooks from your device. Make sure to create a back up copy of your company fire before doing major changes into your account.
For a more detailed information, you may check out this article: Resolve Crash Catcher displaying while using QuickBooks for Mac.
If issue persists, I'd suggest contacting our Technical Support Team. An agent will be able to further assist you via a secured remote access session.
Fill me in if you have other questions about customizing your invoice in QuickBooks. I'm always here to help.