I've noticed that, in addition to not being able to link any PNRs created by AA after about February, I am unable to see newly issued e-tickets for previously-liked PNRs (e.g., when a schedule change causes a new ticket to be issued on an old PNR).
I have no insight into who pays what, but I also have to wonder if perhaps AA doesn't want people being able to see details of e-tickets? The TripCase eticket display is more detailed than what AA shows. The lack of detail makes it impossible to verify that AA correctly calculated EQM, EQD, and RDM.