WordPress - user record URL doesn't show for one user. Can't see why?
I've seen this happen when there are multiple WordPress accounts using the same email address.

These values are stored in the civicrm_uf_match table of the database.  If my first suggestion doesn't pan out, you may want to browse that table and look for duplicate values for contact_id and uf_id (the "WordPress user id") corresponding to this user.  Delete the offending record(s) in this table and let CiviCRM recreate them.