Can't change my seat selection on KLM
I have travel booked from US to Europe and back on Delta through KLM metal, both are 777s. I want to change my seating to windows, and I see several are open, but neither the Delta or KLM website will let me. I don't have no idea why not. Would appreciate any help/thoughts - I really want to grab a window before they are all taken. Thanks in advance.