Graphite shows "None" for all data points even though I send it data

I encountered the same issue using that same puppet module. I'm not exactly sure why, but changing the default retention policy appears to fix it, e.g.

class { 'graphite':
  gr_storage_schemas => [
    {
      name       => 'carbon',
      pattern    => '^carbon\.',
      retentions => '1m:90d'
    },
    {
      name       => 'default',
      pattern    => '.*',
      retentions => '1m:14d'
    }
  ],
}