You cannot publish (or unpublish) this asset because there are no Destinations or WordPress Connectors available.

This error message means that the User trying to publish (or unpublish) does not belong to an applicable group in any of the Site's Destination settings. 

To solve:

1. Click Manage Site and then select Destinations.
   
2. Edit the Destination or Destinations to which the User needs to publish.
3. Verify that the User belongs to a Group in the Destination's Applicable Groups field (and if they do not, add their Group to this field).