Sign out error Cloud Firestore. The caller does not have permission to execute the specified operation

I have a flutter app where I have signed in users successfully and no errors are thrown up. But, when I attempt FirebaseAuth.instance.signOut() in one of my buttons, it signs the user out but throws up this error. I have attached my cloud firestore rules below.

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
  
    match /merchants/{document=**} {
      allow read;
    }
    match /all_merchants/{document=**} {
      allow read;
    }
    match /Types/{document=**} {
      allow read;
    }
    match /Promotions/{document=**} {
      allow read;
    }
    match /search_types/{document=**} {
      allow read;
    }

    
    match /users/{userId} {
      allow read, update, delete: if request.auth.uid == userId;
      allow create: if request.auth.uid != null;
      
      match /{document=**}{
        allow read, update, create, delete: if request.auth.uid == userId;
      }
    }
    
     match /users/{email} {
      allow read, update, delete: if request.auth.token.email == email;
      allow create: if request.auth.token.email != null;
      
      match /{document=**}{
        allow read, update, create, delete: if request.auth.token.email == email;
      }
    }
    
    
  }
}

(edit): My Flutter code for the button is as below:

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';


class SignOut extends StatelessWidget {

  FirebaseAuth auth = FirebaseAuth.instance;


  @override
  Widget build(BuildContext context) {

GestureDetector(
      onTap: (){
          setState(() {
                auth.signOut();
               });
            },
      child: ListTile(
        dense: true,
        leading: Icon(Icons.exit_to_app, color: Colors.red[600], size: 25,),
        title: Text('Sign Out',
                    style: TextStyle(fontFamily: 'Lato', fontSize: 18, fontWeight: FontWeight.w500),),
        trailing: Icon(Icons.arrow_forward_ios, color: Colors.black, size: 19,),
      ),
    );
}
}