ReactJs | axios.request doesn't await

I created this reactjs app.

In this app there is a singleton class "ServerMgr" that I use to send post request to my server.

Previously I used the js fetch function and it worked fine, but now I need to replace it with axios.

I replaced it but even if I set the async/await, it doesn’t wait for the await.

I explain the situation:
in App.js there is this useEffect triggered when the component is mounted that after creating the ServerMgr singleton, call the function getServerMgr().getFullData().

The function getFullData() is an async function that should await the function requestFetchData() to receive the data from the axios request before returning.

The problem is that getFullData() doesn’t await and go ahead without receiveing the request response so the variable appointmentsResults in the useEffect is undefined.

Using the debugger I confirmed that the axios request is correct because it receives the correct data in the .then but after getFullData() went on.

Can you help me?

Here the code:

ServerMgr

 serverMgr.requestFetchData = async (service, args) => {

    let data = args
                ?
                JSON.stringify({
                    "service": service,
                    ...args 
                })
                :
                JSON.stringify({
                    "service": service
                })

    let config = {
        method: 'post',
        maxBodyLength: Infinity,
        url: my_php_script_url,
        headers: { 
          'Content-Type': 'application/json'
        },
        data : data
    };

    axios.request(config)
    .then((response) => {
        return response.data;
    })
    .catch((error) => {
      console.log("ERROR requestFetchData: " + error);
    });
  }

serverMgr.getFullData = async (cb) => {
    let result = await serverMgr.requestFetchData("getAll")
    if(cb) {
        console.log("getFullData: " + result)
        cb(result)
    }
    else {
        console.log("getFullData: " + result)
        return result
    }
}

App.js

 useEffect(() => {
    initSingleton() //this load the singleton
    .then(async () => {
      let appointmentsResults = await getServerMgr().getFullData()
      let appointmentsListClean = removeEmptyAppointments(appointmentsResults)
    })
  }, [])  

  const removeEmptyAppointments = (appoArray) => {
    return appoArray.filter((item) => (item.appointment_id ? true : false))
  }