Image Styles not creating on one custom style only I've run into this issue where we have created a custom style (emailthumb) which is to be used when sending out email newsletters via simplenews. The thumbnail is based on 'thumbnail' style but is slightly bigger. It works fine when the image is being rendered as thumbnail or any other style but not the one custom style.
The permissions of the folders are all exactly the same (I've even tried 777 for emailthumb-&gt;public) as in thumbnail but there is no pictures folder being created. I then get a log error of access denied as the URL to the image as the folder doesn't exist.
http://example.com/sites/default/files/styles/emailthumb/public/pictures/image.jpg
I have tried changing the theme as per
image style (imagecache) images are not being created
but this has not worked.
Does anyone have any suggestions?
Current Permissions
sites/default 555
The problem was that the image style was never being called to save the image in the first place. The following code forces the image to save for this use case.

function MODULE_node_presave($node){
  // Get some field items from a field called 'field_image.
  if ($image_items = field_get_items('node', $node, 'field_image')) {
    $image_item = array_shift($image_items);

    // Load the associated file.
    $file = file_load($image_item['fid']);

    // An array of image styles to create.
    $image_styles = array('emailthumb');

    foreach ($image_styles as $style_name) {
      // Get the location of the new image.
      $derivative_uri = image_style_path($style_name, $file-&gt;uri);
      $style = image_style_load($style_name);
      // Create the image.
      image_style_create_derivative($style, $file-&gt;uri, $derivative_uri);
    }
  }
}


credit here force image style generation on save node