Unable to redeem app codes with Configurator
Do not import the initial VPP spreadsheet into Configurator!

After receiving the initial spreadsheet from VPP, you must redeem one of the codes from the spreadsheet in the iTunes App Store to 'purchase' the app you are distributing. Once you download the app and import it into Configurator, go back to the VPP site and re-download the spreadsheet. This spreadsheet will now have the word Redeemed in the cell where the download link used to be. Import only the second spreadsheet into Configurator.

Lastly, VPP Support is sometimes very forgiving with minor glitches like this and can get you back a license code, especially if the price of the app was substantial.