Firebase App Sign Up Failure: Fatal Error - No ObservableObject of type AuthViewModel found

Question

I'm building an app that uses firebase to authenticate users. I'm trying to sign up a new user and keep getting a fatal error. New to Swift so I'm probably missing something obvious.

Error: Fatal error: No ObservableObject of type AuthViewModel found. A View.environmentObject(_:) for AuthViewModel may be missing as an ancestor of this view. This is focused on my sign up action button where the viewModel is referenced (see just below // end of v).

Sign Up View code:

import SwiftUI

struct SignUpView: View {
    
    @State var firstName = ""
    @State var lastName = ""
    @State var email = ""
    @State var password = ""
    @State var confirmPassword = ""
    
    @Environment(\.presentationMode) var mode
    
    
    @EnvironmentObject var viewModel: AuthViewModel
    
    var body: some View {
        
        ZStack {
            
            BackgroundGradientView()
            
            VStack {
                LogoView()
                    .padding(.bottom, 25)
            
            VStack(spacing:20) {
                
                UserTextField(text: $firstName, placeholder: "First Name")
                UserTextField(text: $lastName, placeholder: "Last Name")
                EmailTextField(text: $email)
                PasswordSecureField(text: $password, placeholder: "Password")
                PasswordSecureField(text: $confirmPassword, placeholder: "Confirm Password")
                
            } // end of V
            .padding(.horizontal, 32)
                
                Button { // sign up action
                    viewModel.register(withEmail: email, password: password, firstName: firstName, lastName: lastName)
                } label: {
                    AuthenticateButtonView(text: "Sign Up").padding()
                }
                
                Spacer()
                
                Button {
                    mode.wrappedValue.dismiss()
                } label: {
                    HStack {
                        Text("Already have an account?")
                            .font(.system(size:14))
                        Text("Sign In")
                            .font(.system(size:14, weight:.semibold))
                    }
                    .foregroundColor(.white)
                }
                .padding(.bottom,16)
            } // end of second V
        }
    }
}

struct SignUpView_Previews: PreviewProvider {
    static var previews: some View {
        SignUpView()
    }
}

AuthViewModel code:

import SwiftUI
import Firebase
import FirebaseAuth

class AuthViewModel: ObservableObject { 
    
    @Published var userSession: User? 
    @Published var currentUser: AppUser? 
    
    static let shared = AuthViewModel()
    
    init() {
        userSession = Auth.auth().currentUser
        //fetchUser()
    }
    
    func fetchUser() {
        guard let uid = userSession?.uid else { return } 
        COLLECTION_USERS.document(uid).getDocument {
            snapshot, _ in
            guard let user = try? snapshot?.data(as: AppUser.self) else { return }
            self.currentUser = user
        }
    } 
    
    func login(withEmail email: String, password: String) {
        
        Auth.auth().signIn(withEmail: email, password: password) { result, error in
            if let error = error {
                print("Login Failed\(error.localizedDescription)")
                return
            }
            
            guard let user = result?.user else { return }
            self.userSession = user
            self.fetchUser()
        }
    }
    
    func register(withEmail email: String, password: String, firstName: String, lastName: String) {
        Auth.auth().createUser(withEmail: email, password: password) {
            result, error in
            if let error = error {
                print("Registeration Failed \(error.localizedDescription)")
                return
            }
            
            guard let user = result?.user else { return }
            
            let data = ["uid": user.uid,
                        "firstName": firstName,
                        "lastName": lastName,
                        "email": email]
            
            COLLECTION_USERS.document(user.uid).setData(data) { _ in
                print("Succesfully uploaded data")
                self.userSession = user
                self.fetchUser()
                
            }
        }
    }
    
    func signout() {
        self.userSession = nil
        try? Auth.auth().signOut()
    }        

}

Again, probably something obvious but would benefit from an explainer.