Dear Sirs, good afternoon.
I just feel that finally I opened my eyes more widely. I have since some time ago the conflict of two commands under the Annotate Tab, namely Filled Region, and Find & Replace. Both show FR in the little banners after pressing Alt-N. Yet Filled Region shows FN, instead of FR, in the tooltip. Maybe it is or was once a synonym of the same command. FR for filled region functions either pressing FR combined or F and R separately. FR for Find & Replace worked for me in anothe Revit version. My only contribution is pointing out something that needs to be checked by you, in my view.
Thank you very much.