@corradoventu - can you provide any more information about that? After clicking "Don't remind me again" on the notification are you getting another notification when you log in again? Can you check if the following is being set to false:
$ gsettings get com.ubuntu.update-notifier notify-ubuntu-advantage-available false -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1959869 Title: Ubuntu Pro subscription notification persists To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/update-notifier/+bug/1959869/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs