React app doesn't display ASP.NET Core / EF Core database data, using Cors to access them (tutorial of Neil Cummings on REACT)

React front is on 3000 and my ASP.NET Core backend is on port 5000. React part has product definition and data fetching from localhost:5000/api and accessing data by prevState in AddProduct function. Based on the tutorial, I have cors to program.cs but I cannot make it work. When running the application, I get

This localhost page can't be found error 401.

Product.tsx

export interface Product {  id: number;  name: string;  description: string;  price: number;  pictureUrl: string;  type?: string;  brand: string;  quantityInStock?: number;}

App.tsx

import { useEffect, useState } from 'react';import { Product } from './product';function App() {  const [products,setProducts] = useState<Product[]>([]);  useEffect(() => {    fetch('htttp://localhost:5000/api/products')      .then(response => response.json())      .then(data => setProducts(data))  },[])  function addProduct() {    setProducts(prevState => [...prevState,      {        id: prevState.length + 101,        name: "product" + (prevState.length + 1),        price: (prevState.length * 100) + 100,        brand: 'some brand',        description: 'some description',        pictureUrl: 'http://picsum.photos/200',      }])}  return (<div className="app"><h1>RESTORE</h1><ul>        {products.map(product=>(<li key={product.id}>{product.name} - {product.price}</li>        ))}</ul><button onClick={addProduct}>Add product</button></div>  );}export default App;

Program.cs:

using API.Data;using Microsoft.EntityFrameworkCore;using Microsoft.EntityFrameworkCore.Migrations.Operations;internal class Program{    private static void Main(string[] args)    {        var builder = WebApplication.CreateBuilder(args);        builder.Services.AddControllers();        builder.Services.AddEndpointsApiExplorer();        builder.Services.AddSwaggerGen();        builder.Services.AddDbContext<StoreContext>(opt =>        {            opt.UseSqlite(builder.Configuration.GetConnectionString("DefaultConnection"));        });        builder.Services.AddCors();        var app = builder.Build();        // Configure the HTTP request pipeline.        if (app.Environment.IsDevelopment())        {            app.UseSwagger();            app.UseSwaggerUI();        }        app.UseCors(opt =>        {            opt.AllowAnyHeader().AllowAnyMethod().WithOrigins("http:/localhost:3000");        });        app.UseAuthorization();        app.MapControllers();        var scope = app.Services.CreateScope();        var context = scope.ServiceProvider.GetRequiredService<StoreContext>();        var logger = scope.ServiceProvider.GetRequiredService<ILogger<Program>>();        try        {            context.Database.Migrate();            DBInitializer.Initilize(context);        }        catch (Exception ex)        {            logger.LogError(ex, "A problem occurred during migration");        }        app.Run();    }}

I have tried to check if my Cors correctly written and if referenced local port are correct.