Lubuntu 18.04 + x11vnc

Hi,
for my Work i must install an configure a Linux Workstation with Lubuntu.
Normally everthing works fine, except 1 thing.
I installed my Lubuntu with a gui (standard) and install x11vnc. When i start x11vnc with the gui, everthing works fine, i can connect to the workstation.
But now, i will start him automaticaly. So far so good.
It starts…but i cant connect to the system, every time it sayd me that he cant connect, because the security settings are wrong.
I tried so many tutorials at this and last day, and i dont know how it can be that i cant remot control my Workstation.
Has anyone an idea?