Consider following code

use mongodb::{{color:#000000}Client, options::ClientOptions{color}};
use mongodb::options::{{color:#000000}Credential, AuthMechanism{color}};

#[tokio::main]async fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut client_options = ClientOptions::parse("mongodb://5.55.55.55:27017").await?;
client_options.credential = Some(Credential::builder().username("docDev".to_string()).password("pass".to_string()).mechanism(AuthMechanism::ScramSha1).build());
let client = Client::with_options(client_options)?;
let db = client.database("documentsDev1");
let collection = db.collection("Orders");
println!("{:?}", collection.find_one(None, None).await?);
Ok(())
}

Which produces following results:

Error: Error { kind: AuthenticationError

{ message: "SCRAM failure: Authentication failed." }

, labels: [] }
error: process didn't exit successfully: `target\debug\untitled13.exe` (exit code: 1)

But I'm able to login from the same machine with the same credentials via C# driver and/or Robo3T