SecureVNC: Reverse connect with public key not working

[Maniaxx]

Hallo,
on the server (win7) i have installed winvnc as a service. In 'uvnc_settings.exe' i have disabled 'Password required', 'SecureVNCPlugin.dsm' selected and generated public/private keys (no password set). The server has '20151222_Server_ClientAuth.pubkey' and the client '20151222_Viewer_ClientAuth.pkey' in their corresponding UVNC folders.

The client starts a listening daemon with ' vncviewer.exe -dsmplugin SecureVNCPlugin.dsm -listen 12345' and the server initiates the connection with 'winvnc.exe -connect client.com::12345'.

Then, on the client a windows pops up asking for a password(?). Why are the public/private keys not used? I've tried to delete the passwords (as stated in another thread) in ultravnc.ini but it seems useless as they are re-set every time i start winvnc.exe.

The server is not connectable from outside and i need UAC control. Not sure if that's possible with SC as well.

1) How can i reverse connect with public/private key without entering a password?
2) Is it not possible to control the user switch screen (user logged out) on Win7?

Edit: Looks like this is related. Could need a blank password option indeed.
Edit2: Seems to work when entering a password in SecureVNCPlugin. WinVNC passwords seem not be relevant (they can differ).