Originally Posted by
ttuna3
Might be a TSA related issue from the US, I've always having issues getting checked in for the US legs before 24 hours even with a US carrier. Coming from outside the US without a connection usually only CBP gets involved and they don't usually seem to have issues with checking in 48 hours before departure. Pre clearance might be an issue (Canada/ Dublin) since you don't have to go through the TSA in the US after arrival.
Thank you ttuna3 for your reply. I also suspect it may have something to do with flights leaving from the US. However, it all ended well for my relative. I checked her booking about 12 hours before departure from LAX and discovered that they allocated her reasonably good seats for the 2 flights. In fact the seat allocated for the long haul from LAX to TPE was the one I was trying to get for her - aisle seat in the middle section of Y cabin, over the wing so not much motion sickness.