1 hour before. It’s very strange that you’re getting conflicting information and to top it off the online check-in doesn’t work. You mentioned below that there may be A delay and a missed flight. The silver lining of that option is that you get the check-in worked out, but I imagine it screws up the rest of the itinerary. I always worry about this situation when my wife books us through LAX and we fly in from Vegas on a different airline.