Lost quick search function in X9

I seem to have lost the “quick search” functionality after reinstalling Endnote X9 on a new PC. Whatever I type in the research field, I get “No matching references found”. I am used to the quick search function since X7 or so including X9 (previous installation) and the behaviour seems just not normal.

P.S. the same problem occurs when choosing “Any Field + PDF with Notes” in the Search Panel but the other search options seem to work (e.g. “PDF”).  I have already performed the reinstall-repair without success