The most likely cause for the vTiger error “Sorry! Attempt to access restricted file.” is the $root_directory value in the ‘config.inc.php’ is incorrect or misspelled.

In order to correct it follow the steps below:

  • Go to your vTigerCRM directory
  • Open “config.inc.php” with your favorite text editor
  • Go to line 86 and adjust $root_directory value to correct vTiger directory. Note, that the directory must end with /. It should look something like this – $root_directory = ‘/var/www/vtigercrm/’;
  • If you can't find the root directorey 
    • Open "Index.php" with your favorite text editor add the following code after <?php
    • echo "__dir__";die;
    • It's display the root directory

Hope that helps!