Just to be clear, even though there is an option for VNC in the weavedconnectd installer, we don't install any VNC service on there. You'll have to do that yourself.
Apparently the newest Raspbian images come with RealVNC pre-installed, which by default uses port 5900 rather than 5901 which is the default for tightvncserver.
Use raspi-config to enable VNC (advanced options) and also to boot to desktop.
Run the following command to see what tcp listeners are listening:
pi@raspberrypi:~ $ sudo netstat -apn | grep tcp | grep LISTEN
tcp 0 0 0.0.0.0:5800 0.0.0.0:* LISTEN 15552/vncserver-x11
tcp 0 0 0.0.0.0:5900 0.0.0.0:* LISTEN 15552/vncserver-x11
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 524/sshd
tcp6 0 0 :::5800 :::* LISTEN 15552/vncserver-x11
tcp6 0 0 :::5900 :::* LISTEN 15552/vncserver-x11
tcp6 0 0 :::22 :::* LISTEN 524/sshd
This shows the vncserver-x11 at ports 5800 and 5900. In this case, 5800 is the port for the Java VNC server, so use 5900.
If you are using a different VNC server, you may have to experiment, but this shows you how to determine which tcp ports have listeners on them and which processes are associated with those ports.