Ubuntu 20.04 install - error message when trying to open a remote from the GUI

[jk-helpsys]

Installed using provided instructions on Ubuntu 20.04. GUI front end server allows new connections to be added. However, when trying to open a connection the GUI shows the error "Error: Failed to connect to remote access server". When monitoring the Docker logs for 'some-guacamole' it does not appear that Guacamole ever receives any request from the BastionBox front end.

Trouble shooting so far shows that on http://localhost:8080/guacamole a Tomcat 404 error page is shown "The requested resource [/guacamole/] is not available. The origin server did not find a current representation for the target resource or is not willing to disclose that one exists."