You need to connect server to existing farm in sharepoint. If due to some issue, you disconnected web front-end server from sharepoint farm. After issue resolution, you need to connect web front-end server back to exisiting server farm again.
sharepoint 2019 configuration wizard run using powershell step by step is very important for monthly sharepoint patching activity. Follow step by step to run sharepoint config wizard.
in this post we will discuss how configuration cache clearing sharepoint 2019 is done in on-premise environment step by step