I posted a review, with the relevant spoiler tag. And it went live for about 4 days and received 23 out of 35 positive ratings and then all of a sudden it was gone, when I went to check it said it had been declined. But it was live for several days and receiving positive feedback
I had that happen to me once or twice. If it's a rather new movie, you may expect it to happen more often. My guess is that moviemakers (or producers / studios / whomever) are not satisfied with their fake review teams for new releases, so they also have "report negative review" teams as well.