Unable to open synced realm offline

I am making a React Native app using Realm Sync and I am in dire need of guidance regarding how to use it offline.

This is the bare bone of my code:

import Realm from "realm";
import { getRealmApp } from "../getRealmApp";

// Access the Realm App.
const app = getRealmApp();

const AuthProvider = ({ children }) => {
 
  const [user, setUser] = useState(app.currentUser);
  
    useEffect(() => {

        if (!user) {
            return;
        }

        console.log('> User: ', user.id) // This logs correctly offline

        const config = {
            schema: [User.schema],
            sync: {
            user: user,
            partitionValue: `user=${user.id}`,
            error: errorSync,

            },
        };

        Realm.open(config).then((userRealm) => {
    
        console.log('> User realm open') // This does not log when offline

            const users = userRealm.objects("user");

            const company_id = users[0].company_id

            if (company_id) {
                setCompanyID(company_id)
            }
        }

    }, [user]);

//... then a company realm is open to access data and show on Home Screen.

} 

This works fine when I have connectivity but when I don’t, the userRealm does not seem to open, despite having found the user.id from the app.currentUser (as proven by the logs).

I have read in places things about opening a realm synchronously versus asynchronously but I am not sure how to do this in my case (if indeed it is where the problem comes from).

Many thanks in advance for any help here!