SharePoint Search is a critical Service, which needs to up and running for many things. If the Search is in PAUSED status, then we can't do a crawl.
First We have to verify All the necessary SERVICES are up and running.
Then we have to make sure the account has permission to run a CRAWL.
Also we have to verify the Alternative Access Mapping is set.
If we cant resolve the issue, then have a look of EVENT VIEWER.
There we can see the "Content Plugin can not be initialized" error message. It makes little interesting and I had a look of SEARCH TOPOLOGY.
Then it shows as "Unable to Retrieve Topology Component". Then we can assume PERMISSION issue somewhere.
Then I have found that the Service called "Windows Service - Search Host Controller Service".
That Account is responsible of working with NODE RUNNER and setting up the SharePoint farm topology. So that account needs LOCAL ADMIN privileges. After I have set the PERMISSION for the account,
The Topology Starts working and fine. It displayed all the COMPONENTS correctly with GREEN color.
Then I was able to see CRAWLING options in front of CONTENT SOURCES.
It makes all other related issues sorted and works fine.