Only thing that shows up red is the annoying 'division still preparing', which I always get on naval invasions forever so I am just paying no mind to it anymore. The target are is a valid area chosen from the air invasion planning procedure, so it should be reachable like every other province that shows up green in the planning process. I experimented a bit and was able to do an invasion to the other Okinawa province or Taiwan like normal - sometimes, sometimes it would work only with one division but not with others. Anyway, besides just giving orders and participating battles, you need to keep an eye on your nation’s war industry and resources. I even reloaded older save but it's still the same. One moment, you may be giving orders to a small division in France, and a second later, you’re at the other hemisphere fighting off soldiers from Japan. the button is green, but when I click 'activate', the divisions just sit there forever.

Air superiority is achieved in regions (or there isn't anything going on, which I assume is the same?), the invasion is properly planned, planes are there.

Hi, I really tried to understand why my paratrooper plan just won't work in the situation in picture.