I understand the importance of going back to the old invoice layout in QuickBooks Online (QBO), ahjvnck. I'm here to share insights about this. 

At this time, our product experts are currently in the process of enhancing the new invoice layout to continue rolling out the new invoice experience to some customers and getting feedback in QuickBooks. Thus, this rollout update will gradually change into your QuickBooks Online (QBO) account. 

If you're using QBO Essential and Simple Start, the option to go back to the old invoicing experience is unavailable. However, if you're using QBO Plus and Advanced, you can opt-in until you migrate. 

If the custom form style option is missing from the Gear icon, we can perform some troubleshooting steps to fix this. There are times when the browser is full of frequently accessed page resources, which causes some errors or unusual responses. 

Let's start accessing your account using a different or private browser. You can use either of these shortcut keys:

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

Once logged in, try to run payroll again. If it works, I recommend clearing your browser's cache. Doing so will remove the historical data and access QuickBooks with a clean slate. You can also switch to a different supported browser.

I've added this article for more details about the new updates in invoices layout in QBO, you can click on this link: See what's new with estimates and invoices in QBO.

Don't hesitate to reply anytime if you still have questions or clarifications about the new invoice layout. I'm more than happy to assist you. Take care, and have a great day ahead!