(Redirected) Function keys in combination with other keys failures

My Dell Inspiron 15 function keys is failing to work properly in combination with other keys, e.g in a program where “Shift + F1” is supposed to do something, it just mute the system as if only the F1 key was pressed,
please I need help?

Note: the keys still perform their basic functions like; volume +/-, prev/ffward, mute, brightness adjustment, e.t.c
Just doesn’t work in combination with other keys like “Shift” to perform secondary tasks