After using a mass upload tool such as Feeds or Migrate to populate your site with as much as thousands of nodes, you will need to re – index your site so that SEARCH can be used.
Normally pressing the ‘Re – Index’ button at the default search settings page above (..admin/config/search/settings) would suffice but if the nodes are in the thousands you will need to use Drush instead.
Logged in using ssh, use the drush command
drush search-index
And it will result in this:
It can take up to 4 seconds per 100 indexed nodes so this may take time. Checking admin/config/search/settings again afterwards will show 100% indexed nodes:


