NSTextAttachment not showing

I am unable to get the NSTextAttachment to show for the NSAttributedString returned in the function below.

- (NSAttributedString *) tokenString:(NSUInteger) tokens
{
CGFloat size = 20;
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
attachment.bounds = CGRectMake(0,0,size,size)
attachment.image = [[UIImage imageNamed:@"ContestTokenSmall"] imageScaledToSize:CGSizeMake(size, size)];

NSAttributedString *attachmentString = [NSAttributedString attributedStringWithAttachment:attachment];

NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:[NSString stringWithFormat:@" %ld", (long)tokens] attributes:[self attributedStringAttributes]];
[str insertAttributedString:attachmentString atIndex:0];
return str;
}

The label I'm using is as follows:

- (UILabel *) tokenLabel
{
if (_tokenLabel == nil)
{
    _tokenLabel = [[UILabel alloc] init];
    _tokenLabel.translatesAutoresizingMaskIntoConstraints = NO;
    _tokenLabel.font = [UIFont zbd_boldFontWithSize:13.0];
    _tokenLabel.textColor = UIColor.whiteColor;
    [_tokenLabel setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
    [_tokenLabel setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisHorizontal];
    [_tokenLabel setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
    [_tokenLabel setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisHorizontal];
}
return _tokenLabel;
}

I've tried removing the NSTextAttachment bounds, changing/removing image resizing, and using a different image but nothing I do seems to make an image appear in the label.

Is there something wrong in the code above? Is there a property I need to set in the label to make the image show?

Thanks in advance!

EDIT

How I set the label:

self.tokenLabel.attributedText = [self tokenString:award.topBid];

Log of string:

2018-04-24 16:03:14.579429-0500 TestGame1[44243:1597097] {
    NSAttachment = "<NSTextAttachment: 0x6040002c2e60>";
} 10{
    NSColor = "UIExtendedGrayColorSpace 1 1";
    NSFont = "<UICTFont: 0x7ff0df85ff10> font-family: \"Domus\"; font-weight: bold; font-style: normal; font-size: 13.00pt";
}

Also, I see an empty space where the image should be.

UPDATE 2

The image created with the code below will show in the attributed string, but still none of the pdf or png images loaded from Media.xcassets will show.

CGRect rect = CGRectMake(0, 0, 1, 1);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [UIColor.redColor CGColor]);
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

I figured it out. The problem was with [UIImage imageNamed:@"ContestTokenSmall"]. Since the image was located in the framework the this code is in, I needed to use

+ (nullable UIImage *)imageNamed:(NSString *)name inBundle:(nullable NSBundle *)bundle compatibleWithTraitCollection:(nullable UITraitCollection *)traitCollection NS_AVAILABLE_IOS(8_0);

so that it would get the image from the correct bundle. I was getting the image from the framework's bundle while debugging and that is why the image would show in image views while not showing in the attributed string.