Joomla - Re: JAuthentication::__construct: Could not load authentication libraries

I disabled the plugin - Authentication – Joomla as I thought it was for user logging in the page, not the admin login. It was a big mistake though. To turn this feature on you need to log to Joomla’s database and change published to 1 in the jos_plugins table  in row.Name = Authentication – Joomla (it was row.id = 1 in my case).

UPDATE `your_database_name`.`jos_plugins` SET `published` = '1' WHERE `jos_plugins`.`id` =1;