Why can't I collapse my push notifications when I use Firebase FCM?
const options = { priority: 'high', collapseKey: user_id }; const deviceTokensPromise = db.ref('/users-fcm-tokens/' + user_id).once('value'); deviceTokensPromise.then(tokensSnapshot => { if (!tokensSnapshot.hasChildren()) { return console.log('There are no device tokens to send to.'); } const tokens = Object.keys(tokensSnapshot.val()); console.log(tokens); console.log(payload); return admin.messaging().sendToDevice(tokens, payload, options).then(response => { console.log(response); return removeInvalidFCMTokens(tokensSnapshot, response); }); }); I have a collapse-Key field in my options. When