The error tells you that there is an error but you don´t catch it. This is how you can catch it:
getAllPosts().then(response => {
console.log(response);
}).catch(e => {
console.log(e);
});
You can also just put a console.log(reponse) at the beginning of your API callback function, there is definitely an error message from the Graph API in it.
More information: https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch
Or with async/await:
//some async function
try {
let response = await getAllPosts();
} catch(e) {
console.log(e);
}