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.
Install SSL certificate trusted root certificate Intermediate certificate is required on sharepoint servers which is provided by Certification Authority. SSL is a security protocol that establishes a secure connection by providing encrypted connection between server and client, typically between server and client browser. So, its mandatory to install ssl certificate in servers.