JSONModel's initwithstring not mapping json response values to class' objects automatically

My Json response data is,

[{"user_id":697,"provider":"Manual","user_image":"dummy_image.png"}]

The JSONModel extended class looks like,

@interface CILoginModel : JSONModel

@property (assign, nonatomic)int user_id;
@property (strong, nonatomic)NSString *provider;
@property (strong, nonatomic)NSString *user_image;

@end

And the code, which I used to assign the JSONResponse values automatically to the CILoginModel's objects is,

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //code executed in the background
        //2
        NSString *post = [NSString stringWithFormat:@"email=jil@yopmail.com&password=123456&provider=Manual"];
        NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
        NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[postData length]];
        NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
        [request setURL:[NSURL URLWithString:@"URL GOES HERE"]];
        [request setHTTPMethod:@"POST"];
        [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
        [request setHTTPBody:postData];
        NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
        [[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
            NSString *requestReply = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
            NSLog(@"requestReply: %@", requestReply);
            NSError *dueError=nil;
            CILoginModel* cilLogin = [[CILoginModel alloc] initWithString:requestReply error:&dueError];
            NSLog(@"%@",cilLogin);
            NSLog(@"%@",cilLogin.provider);
            NSLog(@"%@",cilLogin.user_image);
        }] resume];        
    });

But the problem is I always get null for cilLogin and its objects. I'm new to JSONModel and any help will be appreciated thanks!