This issue was killing me for long time, i searched through bing and found out that issue with the AAM settings.

The Alternate Access Mapping default URL should match with the url which you are trying to Crawl in the SPP search Settings Page. Initially the solution was not working, i stopped the Search service, reset the crawled content and changed the AAM settings it worked.

If that is not working can try replace the _/layouts/OSSSearch.aspx to wss search page.