When installing the Addigy agent from the URL, you must first open the .dmg file and run the package (pkg) directly within the folder. Addigy leverages a hidden file that is inside the DMG which helps point your installation to your organization. If you take the .pkg file out to run on its own, the agent will not fully install as it will not know to which organization it belongs within Addigy.
If you have an Addigy account and have additional questions, you can create a ticket by emailing firstname.lastname@example.org.
Alternatively, you can submit a support request within Addigy.