OK, it looks and sounds like you have everything set correctly.
Seems like you might be experiencing the same issue as myself and others. See this thread for example
https://forums.plex.tv/t/trying-to-get-cinema-coming-soon-trailers-to-work-for-almost-2-years/801840
Hopefully one of the Plex staff will stop by your thread to help. You can also try posting in the other thread too.
