You only get the "Rendering of template .... failed" message if NextGen gallery cannot find the template file that you are asking it to use in the "view" directory of this plugin.
So for example lets use the following shortcode:
[nggallery id=1 template=wp-eStore]The "template=wp-eStore" tells NextGen Gallery to use a template file named "gallery-wp-eStore.php" (NextGen Gallery automatically adds "gallery-" keyword there). So you will get the "Rendering of template gallery ...... failed" error message if the "gallery-wp-eStore.php" file does not exist in the "view" directory of the NextGen Gallery plugin.
Here is a list of most common mistakes that users make:
1. The template name is case sensitive, so make sure you are paying attention to the case sensitivity of the file name and the keyword you used in the shortcode. It may be easier for you identify the difference if you put the file name and the shortcode side by side in a text editor and try to see if there is any difference.
2. After you upgrade the NextGen Gallery plugin you will need to re-upload the template file in the "view" directory of the NextGen gallary plugin (the eStore and NextGen gallery documentation that you followed has a section with explanation for this).
3. Do not use UNOFFICIAL NextGen gallery addons that breaks the standard functionality of the NextGen gallery plugin (there are some really badly coded NextGen Gallery addons out there that you should refrain from using). If you are using such addons, please deactivate them temporarily to see the result.
