You can’t open the application because it is in a Time Machine backup

How are you launching the app? If you are using the Dock icon or an alias on your Desktop, the alias or the Dock icon may still be linked to an older version of the app on a backup volume. Then remove the dock icon and add the app again, directly from the Applications folder. And delete any old alias to the app from your Desktop.

Whether it is backing up or not, you cannot open a backup of an app. You could restore the app and then open it from the Applications folder.

If you are trying to open the app from the Applications folder in your startup drive, something is very wrong.