What is the gray flag with a plus sign (+) that turns into a yellow checkmark on my filmography

Hi IMDb community, I have recently added a new film to IMDb. Even though our film is complete and we have a poster uploaded that shows on our film's page (which you can see here -- https://www.imdb.com/title/tt28671886), when I look at my personal IMDb filmography and the filmographies of every one of our cast and crew members, the poster does not show up for our movie, only a gray flag with a + on it. If I click on the "plus sign", it turns into a yellow checkmark, but nothing else changes. When I refresh the page, there's now a yellow checkmark, but still not the poster. Can anyone help me figure out how to get the poster for our movie to appear as it should in all of our contributors' IMDb filmographies? Thank you so much!