Windows 8.1 search not finding Control Panel settings
I had this exact same problem. However the solution wasn't to enable indexing on my SSD.
Counterintuitively, I solved it by simply disabling the Windows Search Service.
As soon as I disabled Windows Search, search worked perfectly again.
My PC is new and I had recently enabled Windows Search when Microsoft OneNote prompted me to.
Given the choice, I went with slower OneNote searches and a working Search charm!
We had been experiencing exactly the issue you described.
Recently we had migrated to using SSDs and as part of that, we disabled the "Allow files on this drive to have contents indexed in addition to file properties" setting on the C drive.
After re-enabling this setting, we found that the Control Panel settings returned in the search results (in both Everywhere and in Settings).