Have a companion pass that is valid through 12/31/2016.

Trying to add a companion to a 1 way trip from Chicago to Liberia on 12/26. When clicking on "add companion" button I receive an error "The requested departure date that you have entered is invalid. Please modify your date and try again. (10032)".

What can be invalid about that? I just added my companion to other flights earlier this month.