UPDATE: I was finally able to get a seat assignment to stick and the other notification has gone away. No idea why. 

Hi I have re-selected seats more than 5x but am still receiving this notice "We were unable to assign one or more of your seats." I also receive a notice with "Airfare must be ticked by" and tomorrow's date. I am assuming these notices are related. 

The Airfare notice appears after I re-select my seat. When I view my travel plans again a few minutes later, the "We were unable to assign one or more of your seats."  notice has re-appeared.