Avalanche fails to connect to VNC Server

Because of reported improved VNC support I have just upgraded my Raspbian Pi from Wheezy to Stretch .

Unfortunately the new VNC server does not play well with the VNC client on RISC OS
An attempt to connect via Avalanche (v.22) gives the message:
“Server aborted connection.
No configured security type is supported by 3.3 VNC Viewer”

Unfortunately the new VNC server does not play well with the VNC client on RISC OS

Problem fixed thanks to previous forum post by Will Ling Mar 17, 2017.
I turned encryption off and changed authentication from unix to VNC.