Do you get this error that says “Access is denied. Verify that either the Default Content Access Account has access to this repository, or add a crawl rule to crawl this repository. If the repository being crawled is a SharePoint repository, verify that the account you are using has “Full Read” permissions on the SharePoint Web Application being crawled.” while performing a crawl in SharePoint environment?
Googling will make you to check the value of “DisableLoopbackCheck” from the registry editor or check if the content access account has access to the DB or check if the content access account has “Full Control” permission in the service application.
Before or after you do all the above, please make sure that you have entered the correct or the latest password of your content access account in the search administration page. In the search service application.