If you see the error message "Unable to connect to the Partizion extension" it means that the app was unable to establish a connection to the Partizion browser extension. This isn't critical, you can still use the Partizion dashboard without a connection to the browser extension, except you won't be able to use any of the tab management, bookmark, pinned tab, sessions, or current tab features.
In order for the Partizion dashboard to be able to connect to the Partizion extension you must ensure that the extension is installed and enabled. In chrome, go to the extensions page and enable Partizion.
Make sure the Partizion extension is enabled and then try reloading the dashboard to connect.