Hi Ralf, it can depend on a few things, but I’d like to point a few common reasons why this may be happening. First, make sure that you are searching for the right entities. If you click on the downwards arrow on the right of the search icon of the search bar, you can select what entities to search for. Secondly, you need to ensure that you have proper keywords set for the entity you’re searching for. Hope this helps.

Hi David,

Thx a lot for your hints and suggestions.

it helps for understanding.

and also after deeper investigation the finding was : 

it is good to reset the Index from Search server (Stop Searchserver service and restart to deploy the Indexes again)

Ralf