http://localhost:3000/cards not loading but I can see the sides of the cards. Not sure where I went wrong?

  const express = require('express');
const router = express.Router();

//get method is used to handle the Get requests to a certain url
//this callback will run when the client requests this route
router.get('/',(req, res) => {    //location parameter, anonymous callback function
    const name = req.cookies.username;
    if (name) {
        res.render('index', { name }); //The response object's `render` method takes the name of a template as its first parameter
    } else {
        res.redirect('/hello');
    }
}); 

router.get('/hello',(req, res) => { 
    const name = req.cookies.username
    if (name) {
        res.redirect('/'); 
    } else {
        res.render('hello');
    }    
}); 

router.post('/hello',(req, res) => { 
    res.cookie('username', req.body.username) //this will send a cookie to the crowser after we submit the form
    res.redirect('/'); 
}); 

router.post('/goodbye',(req, res) => { 
    res.clearCookie('username');
    res.redirect('/hello'); 
}); 

module.exports = router;

const express = require('express');
const router = express.Router();

//get method is used to handle the Get requests to a certain url
//this callback will run when the client requests this route
router.get('/',(req, res) => {    //location parameter, anonymous callback function
    const name = req.cookies.username;
    if (name) {
        res.render('index', { name }); //The response object's `render` method takes the name of a template as its first parameter
    } else {
        res.redirect('/hello');
    }
}); 

router.get('/hello',(req, res) => { 
    const name = req.cookies.username
    if (name) {
        res.redirect('/'); 
    } else {
        res.render('hello');
    }    
}); 

router.post('/hello',(req, res) => { 
    res.cookie('username', req.body.username) //this will send a cookie to the crowser after we submit the form
    res.redirect('/'); 
}); 

router.post('/goodbye',(req, res) => { 
    res.clearCookie('username');
    res.redirect('/hello'); 
}); 

module.exports = router;

const express = require('express');
const router = express.Router();
const { data } = require('../data/flashcardData.json');
const { cards } = data; // same as const cards = data.cards;

router.get( '/', ( req, res ) => {
const numberOfCards = cards.length;
const flashcardId = Math.floor( Math.random() * numberofCards );
res.redirect(`/cards/${flashcardId}?side=question`)
});

//pass in an object{}, passing the property prompt 
router.get('/:id', (req, res) => { 
    const { side } = req.query;
    const { id } = req.params;

    if ( !side ) {
        res.redirect(`/cards/${id}`);
    }

    const text = cards[id][side];
    const { hint } = cards[id];

    const templateData = { id, text };

    if (side === "question") {
        templateData.hint = hint;
        templateData.sideToShow = 'answer';
        templateData.sideToShowDisplay = 'Answer';
    } else if ( side === 'answer' ) {
      templateData.sideToShow = 'question';
      templateData.sideToShowDisplay = 'Question';
    }

        res.render('card', templateData);   
}); 

module.exports = router;

//require Express module and assign to a variable
const express = require('express');
const cookieParser = require('cookie-parser');

// create Express application and assign it to a variable
const app = express();

app.use(express.urlencoded()); // middleware for parsing http payloads
app.use(cookieParser());

//tell Express to use Pug Template Engine
app.set('view engine', 'pug');

const mainRoutes = require('./routes');
const cardRoutes = require('./routes/cards');

app.use(mainRoutes);
app.use('/cards', cardRoutes);

app.use((req, res, next) => {   
    const err = new Error('Not Found');
    err.status = 404;
    next(err);
});

app.use((err, req, res, next) => {
    res.locals.error = err;
    res.status(err.status);
    res.render('error', err);
    next();
});

//setup development server
app.listen(3000, () => {
    console.log('The application is running on localhost:3000')
});