Can't choose seats on Iberia flight booked via AA
 

I have round trip economy plus tickets from JFk-MAD coming up this october. I booked through AA, the return flight is Iberia codeshare. If I try to select seats for the return it takes me to the Iberia website where it says:

This flight does not permit seat selection

How is that possible? My experience in general with Iberia's website is awful (I've tried registering multiple times and can't do to a number of 'connection errors'), but surely they must have seat selection, especially for Premium Economy tickets.

Anyone know whats going on here or what I should do?

EDIT: Ok, this is way easier than I thought. There's an inconspicuous 'book' button on the bottom of the screen. This actually takes you to a seat assignment screen and I was able to select. Probably a translation error on their website.

I'll leave this post here in case anyone else ever has the same confusion.