PERN Application with React Router -- WebSocket connection to 'xxx' failed:

const App = () => {
  return (
    <>
      <ToastManager />
      {/* <ToastManager toastStack={toastStack} /> */}
      <Routes>
        <Route path="/" element={<Landing />} />
        <Route path="about" element={<About />} />
        <Route path="contact" element={<Contact />} />
        <Route path="signup" element={<Signup />} />
        <Route path="login" element={<Login />} />
        <Route path="dashboard" element={<Dashboard />} />
        <Route path="suppliers" element={<ManagerSuppliers />} />
        <Route path="materials" element={<ManagerMaterials />} />
        <Route path="transactions" element={<ManagerTransactions />} />
      </Routes>
    </>
  );
};

ReactDOM.render(
  <BrowserRouter>
    <ToastProvider>
      <UserProvider>
        <App />
      </UserProvider>
    </ToastProvider>
  </BrowserRouter>,
  document.getElementById("root")
);