Error: No Access-Control-Allow-Origin

Question

[HELP] I am not being able to access my server’s JSON; I’m using this code to access, when I use the urlSrt, it returns me normally, (it is a site that receives a cep and returns a json with the information); But when I try it on my not working api.

$(document).ready(() => {
console.log("Página carregada");
$("#descricao").focusout(() =>{
const cep = $("#descricao").val();

const urlStr = "https://viacep.com.br/ws/" + cep + "/json/";
const urlStr2 = "ip" + ":3000/categorias/1";

$.ajax({
url: urlStr2,
type: "GET",
dataType: "json",
crossDomain : true,
success: (data) => {
console.log(data);
},
error: ((error) => {
console.log(error);
})
})
});
})´´´

I checked some tutorials that said to release the permission , but it still didn’t work.;

app.use(function(req, res, next) {
res.header('Access-Control-Allow-Origin', "*");
res.header('Access-Control-Allow-Methods','GET,PUT,POST,DELETE');
res.header('Access-Control-Allow-Headers', 'Content-Type');
next();
})´´´

Finally, I’m out of ideas