Mouse doesn't work on xvfb

I am on ubuntu 18.04 (sadly, because of external considerations - EC2). I run the following lines:

sudo /usr/bin/Xvfb :0 -ac -screen 0 1024x768x24 &
/usr/local/bin/x11vnc -dp -noxdamage -geometry 1024x728 -ncache 10 -ncache_cr -viewpasswd remote_view_only_pass -passwd XXXXX  -display :0 -forever -shared -logappend /var/log/x11vnc.log -bg -noipv6

(Xvfb seems to be version 1.19.6) (x11vnc: 0.9.16 lastmod: 2019-01-05) And I connect using VNC Viewer . Following that, I get a mouse that seems to move , but not click. But actually the mouse position in the log (notice the dp) stays constant and it doesn't work. cursor_position: set screen pos x=512 y=364