Having been bumped from CW to PE the last time we went to Antigua, I was going to pay for seat selection for the overnight return leg.

When I go into MMB, I get this message

"Visit the website of the airline you're flying with to select your seats. You may be able to do this before check in."

This is a BA flight, on the BA website in MMB. There is then no button to click that says "Choose seats." This is however there for the outbound leg?!

Any ideas?