emacs 26.1: ediff navigation/control window ?

[jonetsu]

Hello,

I'm trying to use ediff on two files loaded in their buffers, from the
menu, choosing ediff -> Two Buffers.  The command executes, and one
file is now marked with white lines of differences.  But there's no
control window to easily navigate through the differences.  Several
ediff buffers were created, like ediff-diff, ediff-errors (empty) and
Ediff Control Panel, also empty.

What is the procedure to be able to make appear the ediff
control/navigation window and therefore use simple commands such a 'n'
and 'p' to navigate through the diff output ?

Cheers.