According to Expertflyer AF652 CDG-RUN is to be operated by a B77W on that date. No award or paid seats are available in Business class (They are in Economy, so the flight seems to be operating), and the seat map confirms that all business class seats have been assigned (but not blocked).

There is very little you can do I'm afraid. If the e-ticket is valid (Theoretically you could give them a call to double check that) then you are booked on that flight. You also may want to double check the fare code to make sure that you have been rebooked into business class. However I do agree that it is a little odd, as normally some seats are blocked and this prevents you from assigning seats beforehand. In this case no seats seem blocked, rather all seats seem to have been selected by other passengers.