Having the same issue,

and related issue, that it can't even pass the paramenter, as the same the user authentication is also not being passed to the cloud.

// Function to call
void calll() {
    final HttpsCallable callable =
        FirebaseFunctions.instance.httpsCallable('hiDear');
    callable.call({"name": "Anwar"}).then((result) {
      // Handle result here
      print(result.data);
    }).catchError((error) {
      print('Error calling function: $error');
    });
  }


// Cloud Function

const functions = require("firebase-functions");

exports.hiDear = functions.https.onCall((data, context) => {
  const name = data.name;
  return `Hello mr. ${name}`;
});



____________________________________________________________
I/flutter (20767): Hello mr. undefined