International Management - Adding & removing players from squads

[A-BombFM]

I want to manage some of the nations in the World Cup, but I want to use the same squads that have been announced for the tournament IRL.

When I go to remove players from the international squad and add those that I want, either the "add player to squad" button doesn't do anything or isn't there at all. Also removing players from the national squad doesn't seem to work either. Adding and removing them from the national pool does nothing.

I'm new to international management so would someone enlighten me if I'm doing something wrong?