The browser addon is not connecting to the SSO agent.
Check the following points:
Is the SSO agent started and a user logged in?
Is the port configured the same on the agent and in the addon?
Is the port open?
In case of connection problems, it can help to reset the settings of the addon and the SSO agent, so that a new pairing takes place.
If a proxy is configured in the browser, the option "Bypass proxy for local addresses" must be activated.