Firebase functions for loop async await

I'm trying to do a relatively simple, in theory, function using Firebase Functions.

Specifically:

• Add + 1 to a realtime database variable for all users

• Send a notification to all users

I'm still trying to understand async/await which is probably why I'm struggling so much with this.

Here is what I'm doing:

 exports.gcIncrement = functions.database
  .ref('gthreads/{threadId}/messages/{messageId}')
  .onCreate(async (snapshot, context) => {

    const data = snapshot.val();
    const threadId = context.params.threadId;
    const uid = context.auth.uid;
    
    adb.ref('gchats/' + threadId).once('value').then(async (gchatData) => {
    const parent = gchatData.val();
    incrementUser(parent.users, uid, threadId); //parent.users is an object with 1-30 users.
    sendGCNotification(parent.users, data);
    return true;
  }).catch(error => console.log(error))
});

And then I have the function incrementUser:

function IncrementUser(array, uid, threadId) {
    for (const key in array) {
      if (key != uid) {
        const gcMessageRef =
        adb.ref('users/' + key + '/gthreads/' + threadId + '/' + threadId+'/unread/');
        gcMessageRef.transaction((int) => {
          return (int || 0) + 1;
      }
    }
  }

and the function sendGCNotification:

  function sendGCNotification(array, numbOfMsg, data) {
    let payload = {
      notification: {
        title: 'My App - ' + data.title,
        body: "This is a new notification!",
      }
    }
    const db = admin.firestore()
    for (const key in array) {
      if (!data.adminMessage) {
        if (array[key] === 0) {

          const devicesRef = db.collection('devices').where('userId', '==', key)

          const devices = await devicesRef.get();
          devices.forEach(result => {
            const tokens = [];
            const token = result.data().token;
            tokens.push(token)

            return admin.messaging().sendToDevice(tokens, payload)
          })

        }
      }
    }
  }
    

I currently get the error:

'await' expression is only allowed within an async function.

const devices = await devicesRef.get();

But even when I get it error-free, it doesn't seem work. The Firebase Functions log says:

4:45:26.207 PM gcIncrement Function execution took 444 ms, finished with status: 'ok' 4:45:25.763 PM gcIncrement Function execution started

So it seems to run as expected but not fulfill the code as expected. Any ideas? Thank you!