FB.API Callback issue

Hello, I am using Unity 5.5.2f1 pro and facebook's SDK v 7.9.4

I have a script which after login (managed in a previous scene) sends an API request to FB asking for friends, name and email and sends that info as a POST to a php website.

note: Since this is meant for iOS I have to test it on a device so I'm using text in the screen to display info (think of it as a badly implemented print statement).

The problem: In my callback function for FB.API I write in the text Gameobject (aka testTxt) the parsed information from the response which is saved in the Custom UserInfo clss. It display's correctly but the code gets stuck there. It doesn't continue to the next function. HOWEVER, if I delete/comment that line and don't display anything in the text field. The codes does continue to the POST function BUT the information from the API call is not passed, i.e my custom class is empty (leading me to believe the callback function is not called at all).

Im stuck here any help is appreciated. Thanks!

 [Serializable]
 public struct FBData {
     public string first_name;
     public string email;
     public string friends;
     public string id;
 
 }
 
 public class UserManagement : MonoBehaviour {
 
     string urlSaveUserData="some php website";
     public Text testTxt;
     FBData parsedData;
 
     // Use this for initialization
     void Start () {
         //Check if it's the first time the user is opening the app. 
         if (UserInfo.FIRST_TIME) {
             //update text (only used for testing, should be removed in production.) 
             testTxt.text = "Your user id is: " + UserInfo.ID;
             //Perform FB.API call to get User Data.
             getUserData ();
 
             //Save in SQL table. (won't get here if line in getUserData() is active)
             StartCoroutine ("saveUserData");
         } else {
             //do something else.
         }
 
 public void getUserData(){
 
         string query = "me?fields=first_name,email,friends";
         FB.API (query, HttpMethod.GET, Apicallback, new Dictionary<string, string> ());
 
     }
 
     private void Apicallback(IGraphResult result){
         //Parse Graph response into a specific class created for this result. 
         parsedData = JsonUtility.FromJson<FBData>(result.RawResult);
 
         //Pass each field into UserInfo class. 
         UserInfo.EMAIL = parsedData.email;
         UserInfo.FRIENDS = parsedData.friends;
         UserInfo.NAME = parsedData.first_name;
         UserInfo.FACEBOOKID = parsedData.id;
 
                 /*problem area, if I comment line below, then previous information is apparently not stored. If left as is then testTxt displays correct information but code gets stuck there.  */
         testTxt.text = "This is the info from USerInfoInside the APICallback: " + UserInfo.EMAIL + UserInfo.FRIENDS + UserInfo.FACEBOOKID;
     }
 
 public IEnumerator saveUserData() {
         //get user info (this information is EMPTY if line in getUserData() is commented. 
         parsedData.id = UserInfo.FACEBOOKID;
         parsedData.friends = UserInfo.FRIENDS;
         parsedData.first_name = UserInfo.NAME;
         parsedData.email = UserInfo.EMAIL;
 
         //translate data into json
 
         string JsonBodyData = JsonUtility.ToJson (parsedData);
 
         //MAke custom  web request (POST method doesnt seem to work very well, documentation example sends empty form)
         var w = new UnityWebRequest(urlSaveUserData, "POST");
         byte[] bodyRaw = new System.Text.UTF8Encoding().GetBytes(JsonBodyData);
         w.uploadHandler = (UploadHandler) new UploadHandlerRaw(bodyRaw);
         w.downloadHandler = (DownloadHandler) new DownloadHandlerBuffer();
         w.SetRequestHeader("Content-Type", "application/json");
 
         yield return w.Send();
 
 //work with received data...}