The leading cause behind this QuickBooks Error 15720 is indeed the interruption in the update process. You are likely to get the following error message:
QuickBooks Error 15270: The update is missing a file. The update is not successful.
First of all, close all of the background applications that are running in the background.
Restart the QuickBooks application.
Hit the Install Later option that shows up on the new window of your QuickBooks application. This window is known as QuickBooks Update Service.
Go to the Help menu and tap the Update Now button.
Browse and tap on the Reset Updates option.
After that, place a checkmark on the Get Updates box.
Once you receive the confirmation of the Reset dialog box, just tap the OK button.
As soon as the update process is completed, you will get to see a confirmation dialog on the screen.
Now, restart your QuickBooks application as you usually would.
A pop-up dialog box will appear on your screen, tap on the Install Now button. Doing so will start installing the downloaded updates of your application.