You are doing nothing wrong: the add-on uses the --allowed flag, to set allowed IP addresses from the add-on settings.
I gather this sets rpc-whilelist-enabled to true.
By default, allowed IP addresses are *.*.*.* (any address).
I thought the log would show whether a client tried to connect and why it fails to connect, but it does not.
1. Are you trying to connect from within your network, or from outside your network?
2. If you are connecting from outside your network, have you forwarded the web-ui port (9091)?
Thanks again, Thoradia.
I'm trying to connect from within my network and, yes, I also have forwarded the port 9091.