When AB1 was de-listed the shares moved off the CHESS subregister and onto the IssuerSponsored subregister. You should have received two statements from Automic at the time, one under your CHESS HIN showing a movement off, and one with your new Sponsor Issued SRN number showing the movement on.
You can contact Automic and ask them to associate the SRN holding with your user account on their system or I think you can do it online once you are logged in. But you need your SRN number. If you don't have the SRN statement you will need to contact Automic and they will post one out to you.
