json error: expected value at line 1 column 1

[ag039st]

MAC os m3 ,

I used auth application-default login, and Im using the same json ,

but this is failling with json error: expected value at line 1 column 1
no clear of which expected value failed

let config = ClientConfig::default().with_auth().await;
match config {
Ok(con) => {
let client = Client::new(con);
info!("successfully connected ")
}
Err(error) => {
error!("something failed {}",error)
}
}