Preflight response is not successful. Status code: 403. React, Flask and Stripe? - reactjs

Question

I feel like I've looked everywhere for this and can't find my answer!
I've got a React app working with a Node server, but I need to get it to work with a Flask server instead.
This is my React code:
function buy() {
window.scroll(0, 0);
fetch(`${IP}/init_checkout`, {
method: "POST",
headers: {
"Access-Control-Allow-Origin": "*",
"Content-Type": "application/json",
},
body: JSON.stringify({
price_id: 'my_stripe_product_price',
}),
})
.then(res => {
if (res.ok)
return res.json();
return res.json().then(json => Promise.reject(json));
})
.then(({ url }) => {
window.location = url;
})
.catch(e => {
console.error(e.error);
});
}
And, my route in Flask:
#app.route('/init_checkout', methods=['POST'])
#cross_origin(origin="*")
def init_checkout():
data = json.loads(request.data)
price_id = data['price_id']
try:
checkout_session = stripe.checkout.Session.create(
success_url='http://localhost:3000', # noqa
cancel_url='http://localhost:3000/form',
payment_method_types=[
'card', 'sepa_debit', 'sofort', 'ideal'
],
mode='subscription',
line_items=[{
'price': price_id,
'quantity': 1
}],
)
return redirect(checkout_session.url, code=303)
except Exception as e:
print(str(e))
return jsonify({'error': {'message': str(e)}}), 400
In the console, I get the url I'd like to get too, but the app won't automatically direct me there?

Answer 1

Just for reference in case anyone else comes across this or similar ... thanks to hmunoz:
function buy() {
window.scroll(0, 0);
fetch(`${IP}/init_checkout`, {
method: "POST",
headers: {
"Access-Control-Allow-Origin": "*",
"Content-Type": "application/json",
},
body: JSON.stringify({
price_id: 'my_stripe_product_price',
}),
})
.then(res => {
if (res.ok)
return res.json();
return res.json().then(json => Promise.reject(json));
})
.then(({ url }) => {
window.location = url;
})
.catch(e => {
console.error(e.error);
});
}
And, my route in Flask:
#app.route('/init_checkout', methods=['POST'])
#cross_origin(origin="*")
def init_checkout():
data = json.loads(request.data)
price_id = data['price_id']
try:
checkout_session = stripe.checkout.Session.create(
success_url='http://localhost:3000', # noqa
cancel_url='http://localhost:3000/form',
payment_method_types=[
'card', 'sepa_debit', 'sofort', 'ideal'
],
mode='subscription',
line_items=[{
'price': price_id,
'quantity': 1
}],
)
return checkout_session
except Exception as e:
print(str(e))
return jsonify({'error': {'message': str(e)}}), 400