Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed using AFNetworking

The problem comes from response parsing. You are trying to de-serialize a JSON reponse (which MUST be contained in either a NSArray or NSDictionary) however your response is none of the above (Most likely a simple string).

Also, try to set the "allow fragments" to the response serializer.

AFJSONResponseSerializer *responseSerializer = [AFJSONResponseSerializer serializerWithReadingOptions:NSJSONReadingAllowFragments];

May be you need authentication to access JSON response. Set authentication like that:

[manager.requestSerializer setAuthorizationHeaderFieldWithUsername:@"XYZ" password:@"xyzzzz"];

Try this:

AFJSONResponseSerializer *responseSerializer = [AFJSONResponseSerializer serializerWithReadingOptions:NSJSONReadingAllowFragments];[self setResponseSerializer:responseSerializer];

instead of:

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];manager.requestSerializer = [AFJSONRequestSerializer serializer];

AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc]initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];//Request Serializermanager.requestSerializer = [AFJSONRequestSerializer serializer];//Response SerializerAFJSONResponseSerializer *responseSerializer = [AFJSONResponseSerializer serializerWithReadingOptions:NSJSONReadingAllowFragments];manager.responseSerializer = responseSerializer;