I'm having this issue also. My index works, the TOC works, but there are no topics found in the search results. The search function however works in webhelp.
***solved*** check that ITCC.dll has been registered, and if not, register it. This dll is used with the production of HTML help. I found mine here (FM version 2015) C:\Program Files (x86)\Adobe\AdobeFrameMaker2015\fminit\Publisher\HtmlHelp\System32