Your server runs with a PHP version that doesn’t support create_function.
From the PHP manual about create function
Warning This function has been DEPRECATED as of PHP 7.2.0, and REMOVED
as of PHP 8.0.0. Relying on this function is highly discouraged.If you are using PHP 5.3.0 or newer a native anonymous function should
be used instead.
If the plugin is yours I would suggest just that, replace the create_function with anonymous function.
If the plugin is not yours and its a paid plugin, contact the plugin author and alert him of the error, ask him to give you the updated version.
If the plugin is free, you can update the code manually (If you know how), but that can be problematic. When the plugin will be updated your changes will be removed.
If this is the only option, make sure to save the plugin with the changes somewhere safe so if the plugin will be updated you will have the previous plugin version with your fix for quick re-apply.
EDIT
Same code but with anonymous function
static function vksort(&$arr, $valuekey) {
$valuekey = sustr::preg_filter('A-Za-z0-9 ', $valuekey);
uasort($arr, function ($a, $b) use($valuekey) {
return strcasecmp($a[$valuekey], $b[$valuekey]);
});
}