@protocol SendStatusDelegate <NSObject>
@required
-(void)didStatusChanged;

@end // eof delegate protocol

@interface SecondTableViewController : UITableViewController

@property (nonatomic, assign) id<SendStatusDelegate> delegate;

@end

// Status is changed on row click
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (self.delegate) { // This is never called because delegate looks to remain empty
        [self.delegate didStatusChanged];
    }
}

@interface FirstTableViewController : UITableViewController <SendStatusDelegate>

@end

FirstTableViewController.m

// Status is changed on row click
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    SecondTableViewController *secondTableVC = [SecondTableViewController alloc] init];
    secondTableVC.delegate = self;

}

secondTableViewControllerInstance.delegate = self;

@interface FirstTableViewController : UITableViewController <SendStatusDelegate>

SecondTableViewControllerInstance.delegate = self;