Connecting Moodle LMS to a Redis server for Moodle caching

I am trying to connect a Moodle 3.9 website that's hosted on a Windows Server 2019 computer to a Redis instance running on a Red Hat Redis server so that I can configure Moodle to use Redis for caching, but I'm struggling to connect the Moodle site to that Redis service and get the caching working. I've referred to https://docs.moodle.org/402/en/Redis_cache_store, but there's a lot of gaps in that documentation... The 'Installed Cache Stores' page in Moodle shows a green tick for Redis in the Moodle 'Cache administration' page. The Moodle PHPInfo page shows that the PHP Redis module is installed in PHP. In Moodle, under 'Site Admin / Plugins / Caching / Configuration', Redis is displayed on the list of Installed Cache Stores. In Moodle, I've added a Store Instance for Redis and pointed the Server field in that Store Instance to the 'myredisserver.mydomain.com' name of my Redis server. I've also tried the ip address of the Redis server. Under 'Site Admin / Plugins / Caching / Cache Stores / Redis' I've added my Redis Red Hat Linux server name as 'myredisserver.mydomain.com' in the Test Server Field. On the Red Hat command line I enter the: `$redis-cli ping` command and Redis responds with `PONG`, implying that Redis is working. So, why can't Moodle connect to Redis? What am I doing wrong? Do I need to specify the 6379 port somewhere in the Moodle caching configuration? Or is it a linux networking issue that I've missed? Or what else am I missing?