Moodle expert for LMS hosted on our Xneelo environment

We have an existing site which give us the below error:

Fatal error: Uncaught Error: Call to undefined function current_language() in /usr/www/users/projehvusv/moodle/lib/setuplib.php:713 Stack trace: #0 /usr/www/users/projehvusv/moodle/lib/setuplib.php(572): get_docs_url() #1 /usr/www/users/projehvusv/moodle/lib/setuplib.php(363): get_exception_info(Object(ArgumentCountError)) #2 [internal function]: default_exception_handler(Object(ArgumentCountError)) #3 {main} thrown in /usr/www/users/projehvusv/moodle/lib/setuplib.php on line 713