Still fatal error

Hello, even with the latest version, we get the fatal error and cannot get to the admin.

Na řádku č. 163 v souboru /wp-content/plugins/woo-multi-currency/includes/support.php došlo k chybě typu E_ERROR. Chybová zpráva: Uncaught Error: Call to undefined function wp_get_wp_version() in /wp-content/plugins/woo-multi-currency/includes/support.php:163
Stack trace: 0 /wp-content/plugins/woo-multi-currency/includes/support.php(117): VillaTheme_Support->plugin_information() 1 /wp-content/plugins/woo-multi-currency/includes/support.php(550): VillaTheme_Support->remote_get() 2 /wp-content/plugins/woo-multi-currency/includes/support.php(416): VillaTheme_Support->get_ads_data() 3 /wp-includes/class-wp-hook.php(324): VillaTheme_Support->dashboard() 4 /wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 5 /wp-includes/plugin.php(517): WP_Hook->do_action() 6 /wp-admin/includes/dashboard.php(135): do_action() 7 /wp-admin/index.php(15): wp_dashboard_setup() 8 {main}

I need to rollback to 2.1.14 to make the site functioning.