Gst registration for branches

We have branches in five different states with same Service tax registration number as centralized billing, and were filing returns with the main office. The Aces website has generated different user ID's and Passwords for Different states. We are not able to register the branches in additional places of business on GST portal as the State is NON EDITABLE. Do we have to register separately for all the branches in GST portal? will there be different GSTIN for different states? Should we raise different invoices at different branches? we would request you to suggest us in the above said query as soon as possible. Thank you.