"Unable to reach the server" error
Eileen McNaughton wrote:


  It's possible you have FULL_GROUP_BY mode enabled in mysql &amp; that is
  causing problems - the log file should be
  /var/www/vietfeir.com/public_html/wp-content/uploads/civicrm/ConfigAndLog/CiviCRM.4a976861044aadd15e2c85b9.log
  (or similar) and have more error details – eileen 16 hours ago


I removed the ONLY_FULL_GROUP_BY mode and the problem was solved. Thanks, Eileen.