I'm getting the same message, after they changed the time of a flight on me. Change of fleet type but somehow, they moved us from Row 8 on the old plane to Row 25 on the new plane. Called the Mosaic line but there was no place to move me. Actually, they were going to move me to the exit row, but I had to be the one to point out to two different reps that they couldn't do that because my kids will only be 14.
I used to love JetBlue. Now, I book around them when possible.
Mike