F2 hotkey does not work

run QtCreator, open the header of the Buffer class, there is a void clear () method; hover the cursor between the letters l and e in the name of the clear method, press F2 (hotkey to go to the method implementation) and nothing happens. But, if you first press F4 (hotkey go to the cpp file), and then press F4 again to return to the class header, and now F2 works.