You are not entering the nib name for the user Interface:
SuccessOrFailViewController *sfvc = [[SuccessOrFailViewController alloc] initWithNibName:@"SuccessOrFailViewController" bundle:nil];
[self presentViewController:sfvc animated:NO completion:NULL];
For storyboard this is the way to go:
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil];
SuccessOrFailViewController *sfvc = [storyboard instantiateViewControllerWithIdentifier:@"SuccessOrFailViewController"];
[sfvc setModalPresentationStyle:UIModalPresentationFullScreen];
[self presentModalViewController:sfvc animated:YES];
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