Here is the direct, honest reason why:
The file FC2PPV-3620789-2-4K.part10.rar is part of a split archive, likely containing video content from the Japanese adult platform FC2. Because it is "part 10," it cannot be opened on its own; you need all associated parts (Part 1 through Part 10 or more) to successfully extract the full file. Extraction Guide To open this specific file, follow these steps: FC2PPV-3620789-2-4K.part10.rar