It seems you use an obsolete version, Prestashop 1.7.4 can be used with PHP 5.6 minimum and PHP 7.1 maximum : https://devdocs.prestashop.com/1.7/basics/installation/system-requirements/
So you have to change PHP version to PHP 5.6 minimum on cPanel.
Warning : PHP 5.6 support will be dropped in Prestashop 1.7.7 : http://build.prestashop.com/news/announcing-end-of-support-for-obsolete-php-versions/
You have to enable Maintenance Mode on Prestashop : Preferences > Maintenance
Clear cache on Advanced Parameters > Performances
Change PHP Version to PHP 5.6 or PHP 7 < 7.2
Clear cache manualy with FTP by remove all folders and files in /var/cache/ Prestashop will regerate them.