Firebase Authentication using a Custom Authentication System error, "The custom token corresponds to a different audience."

Question

To use the authentication information in the security rules of RealtimeDatabase,
I'm trying Firebase custom authentication.
https://firebase.google.com/docs/auth/admin/create-custom-tokens

I created a custom token on the authentication server.
And I authenticated using the created custom token on Android, but an error occurred.

com.google.firebase.auth.FirebaseAuthInvalidCredentialsException:The custom token corresponds to a different audience.

I looked at this thread, but I am wondering what audience is pointing to and what to do specifically.
Firebase token error, "The custom token corresponds to a different audience."

The token payload looks like this:

{
  "aud": "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
  "iat": 1589453768,
  "exp": 1589457368,
  "iss": "firebase-adminsdk-xxxxx@myproject.iam.gserviceaccount.com",
  "sub": "firebase-adminsdk-xxxxx@myproject.iam.gserviceaccount.com",
  "uid": "groupId-userId",
  "claims": {
    "groupId": "groupId"
  }
}

The example code on the authentication server:

const admin = require('firebase-admin');
admin.initializeApp();

let uid = groupId + userId; // value from client app
let additionalClaims = {
    groupId: groupId
};
admin.auth().createCustomToken(uid, additionalClaims)
    .then(function(customToken) {
        // Send token back to client
        console.log("CustomToken:" + customToken);
        let response = {
            token: customToken,
            companyCode: companyCode,
            userCode: userCode
        };
        res.type('application/json');
        return res.status(200).send(response);
    })
    .catch(function(error) {
        console.log('Error creating custom token:', error);
    });

The example code on the Android:

if(!TextUtils.isEmpty(mCustomToken)) {
    mAuth.signInWithCustomToken(mCustomToken)
            .addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    e.printStackTrace();
                }
            })
            .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    if (task.isSuccessful()) {
                        // Sign in success
                        Log.d(TAG, "signInWithCustomToken:success");
                        FirebaseUser user = mAuth.getCurrentUser();
                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w(TAG, "signInWithCustomToken:failure", task.getException());
                        Toast.makeText(LoginActivity.this, "Authentication failed.",
                                Toast.LENGTH_SHORT).show();
                    }
                }
            });
}