One of the cache hosts in the cluster is down (SharePoint Server)
APPLIES TO: 
2013 2016 2019 Subscription Edition 
SharePoint in Microsoft 365
Rule Name: One of the cache hosts in the cluster is down.
Summary: One of the cache hosts in the cluster is down. This indicates that the SharePoint cache client is trying to connect to the wrong cache host.
Cause: The AppFabric Caching service is stopped.
Resolution: Start the AppFabric Caching service.
Verify that the user account that is performing this procedure is a member of the Administrators group on the local computer.
In Server Manager, click Tools, and then click Services.
In the Services list, make sure that the status of AppFabric Caching Service is Started. If not, right-click AppFabric Caching Service, and click Start.
By default, the Repair Automatically option is enabled for this rule. You can restore the default setting for this rule by doing the following:
Set the Health Analyzer rule to repair automatically
On the SharePoint Central Administration website , click Monitoring.
On the Monitoring page, in the Health Analyzer section, click Review rule definitions.
On the Health Analyzer Rule Definitions - All Rules page, in the Category: Availability section, click the name of the rule.
On the Health Analyzer Rule Definitions page, click Edit Item.
Select the Repair Automatically check box, and then click Save.