dump() not working in Drupal 8 (blank page, debbugging is enabled)
I agree with the comment left for the question: It seems you have an out of memory issue. Check the error log for the server.

I had the same problem with dump() and kint() in an implementation of template_preprocess_views_view_field(), while trying to output the content of a row, on a clean and fresh Drupal 8 installation. 
I found a workaround for kint(), which seems to temporary fix the memory issue. Add the following settings in the config.default.php file for the Kint module.

/** @var int max array/object levels to go deep, if zero no limits are applied */
$_kintSettings['maxLevels'] = 4;


Take it as a hint: Print a specific variable, not the whole array of variables.