SfBApplication *sfb = SfBApplication.sharedApplication;
the sfb always return nil,can you help me ?why?
From the documentation you can read that the return value is :
Shared application instance or @a nil if initialization fails
Have you followed the instructions from here ? Especially the import part :
#import <SkypeForBusiness/SkypeForBusiness.h>
#import "SfBConversationHelper.h"
Have you also added the ConversationHelper
Class to your source ?