Push Notifications on Android: no sound

[masfour7]

I'm using Firebase Cloud Messaging to implement the push notifications feature in my Flutter app. The notification is being received on both iOS and Android as intended. However, although the sound is working on iOS; no sound, vibration, nor pop-up is showing on Android.

It doesn't work using the server with sound set to default (Node.js):

            const message = {
                notification: {
                    title: title,
                    body: body,
                },
                token: androidNotificationToken,
                data: {
                    recipient: users[0],
                    clickAction: "FLUTTER_NOTIFICATION_CLICK",
                },
                android: {
                    priority: "high",
                    notification: {
                        sound: "default",
                    },
                },
                apns: {
                    payload: {
                        aps: {
                            contentAvailable: true,
                            sound: "default",
                        },
                    },
                },
            };

            admin
                .messaging()
                .send(message)
                .then((response) => {
                    // Response is a message ID string
                    console.log("Successfully sent message", response);
                    return null;
                })
                .catch((error) => {
                    console.log("Error sending message", error);
                    return null;
                });

It also doesn't work when I use the Firebase console directly (with sound enabled as shown in the picture): Screenshot of my Firebase console configuration

I also made sure to have sound permissions set to allow on the android phones I tested on.

I'm clueless on how to make the sound work on Android as it's working on iOS? Any help is appreciated.