App Wrapper couldn't find Xcode on your machine. If it is installed on your Mac, first restart your Mac as Spotlight has died. If it still cannot be found, use "Disk Utility" to check for disk errors.
Xcode can be downloaded from the App Store.
Older versions of Xcode can be downloaded from developer.apple.com/download/more/
Please open Xcode, select "Preferences" from the "Xcode" menu. Select "Locations" from the toolbar, and choose a version from the menu next to "Command Line Tools".
Xcode doesn't correctly integrate with your Mac unless it is in the "Applications" folder of your boot volume. Move it there and try again.
As the title suggests, Xcode needs to be at least a certain version for Apple's Notarization service.
Normally Xcode will install all the required tools on launch, or a dialog will pop-up asking to install the "Command Line Tools". If neither occur and App Wrapper displays this error, please manually download the "Command Line Tools" from the following link.