Ok, progressed a little bit.
Connected the notebook to the router (and internet) by a cable.
Used wifi to access the controller.
Set the IP to 192.168.210.100 (DHCP disabled as the site will not always have internet access)
B1 button agrees that the IP is 192.168.210.100
I can access the controller now by wifi but when I plug in the ethernet module (and restart the controller) there is no connection, not even ping works.
I had to trawl through all the forum posts to discover that internet connection is required to access the controller because of Java.
This detail (major detail) should be highlighted in the manual.
Also in the app, what does opensprinkler name mean? there is no explanation, name is not mentioned in the program, or is it meant to be the name of the router/modem.