Originally Posted by UAzip
This has happened to me many times too. One rumor I heard was that if you waited until 23:59:59 before your connecting flight departs, then you don't have the problem. That is, it might be a bug where the OLCI can't change seat assignments for flights beyond 24 hours, even when they are connections from a flight leaving in less than 24 hours. This is just a rumor, though.....
I heard that, too, and used to experience the same problems. I now wait until 24 hours prior to the departure time of my latest connecting flight, and haven't encountered the problem since. It might be a bug, it might be the way the system is intended to work, but whatever it is, it's a pain in my @$$.