Firebase Security Rules - Error getting document: FirebaseError: Missing or insufficient permissions

I'm writing a react application that signs in a user via Google/Facebook using firebase auth and then looks to create a user in the users table if the user doc is not yet in the firestore users table. Per the following code:

function loginSocial(provider) {
    return auth.signInWithPopup(provider).then((res) => {

    //we've signed in and we now want to check if the doc exists in the db
    
    console.log(user.uid, auth.currentUser.uid); 

    var docRef = app.firestore().collection('users', res.user.uid)

    docRef.get().then((doc) => {
    
      if (doc.exists) {
        //if the doc exists then we don't do anything
      } else {
       //code to create user
      }

The issue is that the docRef.get() call is failing - from the console:

> Uncaught (in promise) FirebaseError: Missing or insufficient permissions.

But my firebase rules should be letting it through as I understand it:

rules_version = '2';

service cloud.firestore {
  
  match /databases/{database}/documents {
    match /users/{userId} {
      // allow users to read/update their own document
      allow read, update: if request.auth != null && request.auth.uid == userId;
    }
    
    // allow user to modify collections nested under their own document
    match /users/{userId}/{document=**} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
  }
}

Any ideas why this would be failing and what I can do instead?

Note this is what I see in the console:

Here's the code that ended up working for me, this might be an issue of me using an outdated firebase version

var colRef = app.firestore().collection('users')

colRef.doc(user.uid).get().then((doc) => {
      if (doc.exists) {
        console.log("Document data:", doc.data());
      }
      else{
        //create user
      }
    })