Here's why:
* Missing article: You need an article (a, an, the) before the word "film."
* Incomplete thought: The sentence is incomplete. It needs more information about what film you're asking about.
Here are some correct ways to phrase the sentence:
* Did you see the film?
* Did you see a film?
* Did you see the film about [topic]? (e.g., "Did you see the film about the dinosaurs?")
Let me know if you have any other phrases you'd like to check!