Thanks for posting to the Community, @Yvonne12.
We're unable to revert it to the previous version of QuickBooks 2018 because the update has been installed on your computer. Make sure to uninstall QuickBooks Desktop first before reinstalling the product.
You can follow the steps given to this article for the clean install (whether installing or reinstalling QuickBooks): Clean install QuickBooks Desktop.
Otherwise, you can switch to Selective startup mode so you can install or uninstall the program smoothly by following the steps through this article: Install or uninstall QuickBooks in Selective startup.
If the issue persists, you can contact our Care Support team. They have tools to help you check your account and investigate.
Please let me know if you need further assistance. I'll be around to help. Have a good one!
