This has happened to me on almost every UA F trip I've ever booked. Eventually it clears. But for there to not even be a single award seat when the cabin is empty... don't get me going.

A good agent will try and force connections... building a PNR piece by piece. See if there are any award F seats to the US from CDG through any gateway. Good luck... I thought I was gonna be "stranded" in europe after new years, but everything cleared last week.