How to find the list of 'paths' on my site?
To get all the paths you can use, you can use the following code to get all the paths defined from modules:

$items = module_invoke_all('menu');
drupal_alter('menu', $items);
foreach ($items as $path =&gt; $info) {
  print preg_replace('/%([a-z0-9_]*)/i', '*', $path);
}


The code will show the path as you enter in the block settings; this means it will change node/%node in node/*, and node/%node/edit in node/*/edit.  

About your specific issue, the block could not appear because the block has not been assigned to any theme section, the theme doesn't define the section where the block should appear, or the block is empty. In most cases, modules don't output empty blocks.