Wordpress Problem : Fatal error: Uncaught Error: Call to undefined function

[admin]

I receive an error that you can see in the bottom of my question when trying to open my Wordpress site.

In the FTP directory I have tried to disable all plugins, then also all themes but it does not help.

<blockquote>
Fatal error: Uncaught Error: Call to undefined function
determine_locale() in
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-includes/class-wp-locale-switcher.php:48
Stack trace: #0
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-settings.php(418):
WP_Locale_Switcher->__construct() #1
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-config.php(76):
require_once('/export/sd217/w...') #2
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-load.php(37):
require_once('/export/sd217/w...') #3
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-blog-header.php(13):
require_once('/export/sd217/w...') #4
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/index.php(17):
require in
/export/sd217/www/jp/r/e/gmoserver/5/4/sd1019254/uniq-table.com/wordpress-4.9.2-ja-jetpack_webfont-undernavicontrol/wp-includes/class-wp-locale-switcher.php
on line 48
</blockquote>