Can't get custom fonts to load once successfully registered with CTFontManagerRegisterGraphicsFont, help?

gistfile1.m

NSInteger const FontNotLoadedError = 101;
NSInteger const FontDoesNotExistError = 102;
NSString * const fontErrorDomain = @"FontError";

static NSDictionary *registeredFonts;

+ (UIFont *)customFontNamed:(NSString *)fontName size:(CGFloat)size
{
    UIFont *font;

    if ([registeredFonts[fontName] boolValue])
    {
        font = [UIFont fontWithName:fontName size:size];
    }
    else
    {
        NSError *error = [self loadFontNamed:fontName];
        if (error)
        {
            DDLogError(@"An error occurred loading the font %@. Error: %@", fontName, error);
        }
        else
        {
            font = [UIFont fontWithName:fontName size:size];
        }
    }

    return font;
}

+ (NSError *)loadFontNamed:(NSString *)fontName
{
    if (!registeredFonts)
    {
        registeredFonts = [NSDictionary dictionary];
    }
    if (registeredFonts[fontName])
    {
        return nil;
    }

    NSString *fontFilePath = [listIconsPath() stringByAppendingPathComponent:fontName];
    if ([JFFileManager isFileAtPath:fontFilePath])
    {
        NSData *fontData = [JFFileManager contentOfFileAtPath:fontFilePath];
        CFErrorRef error;
        CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)fontData);
        CGFontRef font = CGFontCreateWithDataProvider(provider);

        NSError *loadingError = nil;

        if (!CTFontManagerRegisterGraphicsFont(font, &error))
        {
            CFStringRef errorDescription = CFErrorCopyDescription(error);
            NSString *errorDescriptionString = (__bridge NSString *)errorDescription;

            if (errorDescriptionString.length > 0)
            {
                loadingError = [NSError errorWithDomain:fontErrorDomain code:FontNotLoadedError userInfo:@{ NSLocalizedDescriptionKey : errorDescriptionString }];
            }

            CFRelease(errorDescription);
        }

        CFRelease(font);
        CFRelease(provider);

        if (!loadingError)
        {
            NSMutableDictionary *mutableRegisteredFonts = [registeredFonts mutableCopy];
            mutableRegisteredFonts[fontName] = @YES;
            registeredFonts = [mutableRegisteredFonts copy];
        }

        return loadingError;
    }
    else
    {
        return [NSError errorWithDomain:fontErrorDomain code:FontDoesNotExistError userInfo:@{ NSLocalizedDescriptionKey : [NSString stringWithFormat:@"No font exists at the resource path %@", fontFilePath] }];
    }
}