Allow me to share information about switching from the old to the new experience.
Since 2023, QuickBooks has been slowly rolling out its updated layout to users. As of October 16, 2023, Simple Start users have been migrated to the new invoice experience, followed by Essentials plan users on December 11, 2023. Furthermore, your account will automatically be updated to the new layout once it's available for it. However, if you've already experienced the new layout and reverted back to the classic one, you may not be able to switch back to the new experience for now. Rest assured, this capability will be available again in the future.
You can find more details about the new layout in these articles:
If you have any other inquiries or need further clarification regarding the transition to the new experience, please feel free to use the reply button. I'm just one post away.