Lost login window

[Changala]

Running Sparky 6.6 on Asus laptop UX305FA (2014)
Have installed Sparky-Mini and LXDE on top of it.

Worked like a charm until I crashed it !
Playing around with Gnome-extension, I made a wrong setup...

It now automatically connects to Openbox.
When I disconnect/logout, I get the background picture, without any means of logging in again,
no window to enter user credentials, no drop-down menu to switch environment,
only way is to power off.

I have tried, with Aptus, to remove, then re-install LXDE, but still no way to switch environment,
no login window after logout.

Is there a way to bring back this login window ?

Thank you