Did you have a seat selected a few days ago? What I think has happened here is that at T-72 hours your service gets moved from one system to another, called FLY and Theoretical Seating kicks in. There is a dedicated thread for TS, so I won't repeat it all here, but if you didn't select a seat beforehand TS has a seat for you, it's just it's a mystery until Online Check-in starts as to which seat. So if the flight is on Sunday night, OLCI starts Saturday night. Also it seems to be a busy flight so TS has more or less blocked the entire seat inventory. This is a dynamic process so if you keep looking other things will happen and it's possible other seat options will show. But at OLCI you will see a seat and probably have a limited number of seats that you can select in addition to the one TS has for you. Bientôt tout ira bien.