I couldn't check in online for CNS-GUM-IAH this week (the link was there) and support also said no synch problems and wasn't SSSS targeted. So maybe co.com can't handle the date line issue either.

Even if I could get online, the online seat map was a mess on CO 1 and CO 2 through flights since I couldn't find a way to see or book better seats beyond HNL on wide open flights when the IAH-HNL-IAH legs were full.