Follow the steps mentioned below to solve your Joomla Issue as this is a well known JOOMLA specific issue:
To fix the one word error: "ERROR" turn the error reporting to maximum by the following steps:
1: In your configuration.php file type : public $error_reporting = 'maximum';
Now you will get the detailed error.
To solve the known JOOMLA specific issue try the following steps:
1: try installing "sudo apt-get install php7.0-xml" and then you have to run the command : --enable-libxml
2: Now restart the apache server by "sudo service apache2 restart"
This should solve your Joomla Issue.