Allow me to provide some more information about maintenance updates.
These updates are contained in each company file that you have through Desktop. This means you'll have to download them through each system separately. The only download option online is the Desktop program which you already have installed on your computer. You can follow the steps below to learn how:
Right-click on the QuickBooks icon and choose Run as Administrator.
Make sure to close all the pages, then navigate to the Help menu, and select Update QuickBooks Desktop.
Go the Options tab and choose Mark All.
Hit the Update Now tab and check the Reset Updates box.
When you're ready click Get Updates.
That's all there is to it. Now you can update all your company files for the maintenance updates. You may find this article about updates helpful as well.
Feel free to comment below if you have any other questions. Enjoy the rest of your week!