Setting knob

i am unable to set N1 or speed reference using the knob on the main panel. The inner knob in the speed reference selector should set the vref or grossweight , while the inner knobin the N1 selector should set the N1 reference bug in the eicas.With The click spot aside the knobs i can move only the outer knob,so when i select for esamble the grossweight position, then i can't set the value for the grossweight.For the N1 setting the same problem.I don't know if it's a bug or this function is not implemented,Thank for any help or suggestionMaury