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.....
That's interesting ... The same thing happened to me on the return leg from FLA. I guess you now should wait until 24 hrs prior to your longest leg to check in.