1.Go to library
2.right click on Rust
3.choose properties
4.go to local files in properties
5.choose verify integrity of game files
Just follow these steps.

nebo

1. Run EasyAntiCheat_setup.exe as an administrator
2. Install, uninstall and install EAC for rust
3. Verfiy Steam cache for Rust
4. Run RustClient.exe as an administrator