I'm creating a platformer and i put the same code on a different enemy sprite (when you attack it and it's health goes down.) I put the same code on a flying enemy but instead it doesn't work.

You need to share the link to the project.

Sharing the project would definitely help. Off the top of my head, though, when you move code between sprites/projects the local and cloud variables break and you have to replace them all (usually).

Using the glide block, nothing can check until the glide block completes. Here is an example showing. https://scratch.mit.edu/projects/393845886/

Best to use the move block and check after each move or use a separate loop to detect collision.

Edit: Looks like you used the move block instead of the glide block in the other 2 sprites that work.