Hi!
As soon as I deactivated quick cache it started to work. I checked the plugin and the caching was deactivated, however it remained active somehow. I have tried to clear the cache but nothing happened, so I deactivated it. Then I made changed to the search plugin, activated caching again, cleared the cache and everything was normal.
Perhaps it’s a bug somewhere in the caching system, or an incompatibility with plugins, I’m not sure. I suppose you should deactivate the cache plugin until you configure the search and other plugins, and switch it back on when you finished.