Drush alias partially working
In drush status you should have the following lines right after Database credentials:

Database                        :  Connected
Drupal bootstrap                :  Successful 


When you don't have it, this suggest your Drupal instance is not properly configured and drush has problem bootstrapping it. For example, you may check if you can connect to the database, try: drush @mysite sqlc.

When executing dd on a remote machine, Drupal needs to be able to bootstrap on the configuration level, so it can read the variables. When you don't have the proper access, you'll have the error like:


  Target 'root' not found.


See also: drush_core_drupal_directory().



Other suggestions:


Make sure that on your local and remote you have got the same version of drush.
Other problems could include issues with specific PHP version (see: #779).
If you've still problems, run drush with verbose (-v) or debug options (-d).