Please could you help and confirm what version of Mac OSX you are using?
Also, please confirm the current driver version by clicking on ActivManager>Control Panel, the driver version is listed at the bottom at the side of the Copyright message.
Should you be using a previous version of ActivManager (current version is 5.12.17) we would recommend uninstalling the current ActivDriver and going to http://www.PrometheanKB.com and searching for article 10902. This will download and install the latest version.
Should you still have issues with no connection, we would recommend testing a known working USB cable directly into the ActivBoard bypassing any wallboxes or extension cables.