The Editor of Football Manager 2017 must be installed in the same parent directory where resides your Football Manager 2017 installation:
For example if you installed FM2017
in D:\Games\Football Manager 2017, the editor must be installed
to D:\Games\Football Manager 2017 Editor.
If for any reason you can’t do that, you’ll need to edit the file “special folders.xml” and set the correct path to your main game installation.