Issues while using payment notification endpoint

I’m triying to use payment notifications endpoint but is not working
[POST] https://store.env.com/api/oms/pvt/orders/{orderId}/payments/{paymentId}/payment-notification
It’s always returning:
{
“error”: {
“code”: “1”,
“message”: “A requisição solicitada está indisponível”,
“exception”: null
}
}

Any insight?

I’m triying to use it because the callback of my payment gateway seems not to be updating the state of the order, so I want to do it manually.

Q2: Which is the flow that I need to run or what should I do after the payment gateway trigger the callback Im using a mobile app, so using the same callback doesnt work.