I think every 30,000 miles is what's in the manual, If a sealed tranny have a Toyota service center do it. Something to do with temperature and a reset ???Or ?
What do you mean by "Purchased as a new car" ? Either the car was new or it wasn't...If the dealer sold this as new I would be at there door step with my lawyer. Let us know the updates please.
I am not familiar with this seal, Does it need to be pressed in ? Is it in backwards meaning should it be flipped over ? Are you sure the surfaces are clean prior to install. Are the seals OEM Toyota ? I wish I was of more help.