You can read more (and apply for the program) here: https://developer.oculus.com/blog/introducing-oculus-start/

• Unity 2017.3.1f1 
• ovr_unity_utilities_1.24.0
  
• OVRPlatformSDK_v1.24.0
  
• ovr_avatar_sdk_1.24.0
  

OVRManager:Awake() (at Assets/OVR/Scripts/OVRManager.cs:904)

using UnityEngine;
using Oculus.Platform;

public class AppEntitlementCheck: MonoBehaviour {

  void Awake ()
  {
    try 
    {
      Core.AsyncInitialize();
      Entitlements.IsUserEntitledToApplication().OnComplete(EntitlementCallback);
    } 
    catch(UnityException e) 
    {
      Debug.LogError("Platform failed to initialize due to exception.");
      Debug.LogException(e);
      // Immediately quit the application.
      UnityEngine.Application.Quit();
    }
  }

  void GetEntitlementCallback (Message msg) 
  {
    if (msg.IsError) 
    {
      Debug.LogError("You are NOT entitled to use this app.");
      UnityEngine.Application.Quit();
    } 
    else 
    {
      Debug.Log("You are entitled to use this app.");
    }
  }
}

Could you explain to me why these error still appearing and if there's a solution? 

I'll give thanks to everyone who support me in this topic.

https://www.assetstore.unity3d.com/en/#!/content/10333

The Oculus VR Starter Kit Has Been Released!! This package gives you a solid Framework to run around in your VR Environment and Interact with Objects.
I wrote this for my students in the VR classes I teach, originally. The goal was to get students past the technical stuff quickly so they could go straight to telling their stories. Now in a couple of minutes they can walk around and use objects in their environment.
Also in the past, with supplied scripts, there were problems with memory issues in Unity. By writing all the code myself, I was able to remove all these issues.
And of Course, Since this code is constantly being used in both Class and Production Environments, It will always be updated with new features.

I hope people Enjoy the kit and I look forward to seeing all the cool stuff people make with it.

SessionSettings = MakeShareable(new FOnlineSessionSettings());

			SessionSettings->bIsLANMatch = bIsLAN;
			SessionSettings->bUsesPresence = bIsPresence;
			SessionSettings->NumPublicConnections = MaxNumPlayers;
			SessionSettings->NumPrivateConnections = 0;
			SessionSettings->bAllowInvites = true;
			SessionSettings->bAllowJoinInProgress = true;
			SessionSettings->bShouldAdvertise = true;
			SessionSettings->bAllowJoinViaPresence = true;
			SessionSettings->bAllowJoinViaPresenceFriendsOnly = false;

			SessionSettings->Set(SETTING_MAPNAME, FString("NewMap"), EOnlineDataAdvertisementType::ViaOnlineService);

			// Set the delegate to the Handle of the SessionInterface
			OnCreateSessionCompleteDelegateHandle = Sessions->AddOnCreateSessionCompleteDelegate_Handle(OnCreateSessionCompleteDelegate);

			// Our delegate should get called when this is complete (doesn't need to be successful!)
			return Sessions->CreateSession(*UserId, SessionName, *SessionSettings);

OculusFriend.bIsPlayingSameGame = Presence.bIsPlayingThisGame;
OculusFriend.bIsJoinable = Presence.bIsJoinable;

// Now that we are sure that everything worked, try to actually get the FriendList
      TArray<TSharedRef<FOnlineFriend>> FriendList;
      FriendInterface->GetFriendsList(LocalUserNum, ListName, FriendList);

      // Iterate over the FriendList and fill in all Data into our Dummy Struct
for (TSharedRef<FOnlineFriend> Friend : FriendList)
{
  // Get Presence State
  FOnlineUserPresence Presence = Friend->GetPresence();
  // Dummy Array Entry
  FOculusFriend OculusFriend;

  OculusFriend.DisplayName = Friend->GetDisplayName();
  OculusFriend.RealName = Friend->GetRealName();
  OculusFriend.StatusString = Presence.Status.StatusStr;
  OculusFriend.bIsOnline = Presence.bIsOnline;
  OculusFriend.bIsPlaying = Presence.bIsPlaying;
  OculusFriend.bIsPlayingSameGame = Presence.bIsPlayingThisGame;
  OculusFriend.bIsJoinable = Presence.bIsJoinable;
  OculusFriend.bHasVoiceSupport = Presence.bHasVoiceSupport;
  OculusFriend.PresenceState = (EOnlinePresenceState::Type)(int32)Presence.Status.State;
  OculusFriend.UniqueNetID = Friend->GetUserId();

  OculusFriendList.Add(OculusFriend);
}

Friend->GetDisplayName();

Presence.bIsOnline;