500 Internal Server Error when enabling Redis on Moodle

Hello, I’m trying to enable Redis on my Moodle installation by adding the following settings to my config.php file:

//$CFG->session_handler_class = '\core\session\redis';
$CFG->session_redis_host = '';
$CFG->session_redis_port = 6379;  // Optional.
$CFG->session_redis_database = 0;  // Optional, default is db 0.
$CFG->session_redis_auth = ''; // Optional, default is don't set one.
$CFG->session_redis_prefix = ''; // Optional, default is don't set one.
$CFG->session_redis_acquire_lock_timeout = 120;
$CFG->session_redis_lock_expire = 7200;
$CFG->session_redis_lock_retry = 100; // Optional wait between lock attempts in ms, default is 100.
//                                    // After 5 seconds it will throttle down to once per second.
//Use the igbinary serializer instead of the php default one. Note that phpredis must be compiled with
//igbinary support to make the setting to work. Also, if you change the serializer you have to flush the database!
$CFG->session_redis_serializer_use_igbinary = false; // Optional, default is PHP builtin serializer.
$CFG->session_redis_compressor = 'zstd'; // Optional, possible values are:
//                                       // 'gzip' - PHP GZip compression
//                                       // 'zstd' - PHP Zstandard compression

However, when I uncomment the first line ($CFG->session_handler_class = '\core\session\redis'; ), I get a 500 Internal Server Error. There are no error messages in my logs. If I leave first line commented, Moodle loads fine but I see 0 hits and 0 everything in redis-stats (lightweight dashboard to show statistics about a Redis server).


PS. Redis is working fine with a WordPress installation on a different subdomain on the same server.

Has anyone encountered a similar issue when trying to use Redis with Moodle? Any help would be greatly appreciated.

Bump, in case someone can help. Thank you

It make sense to ask the developers of Moodle instead