Documentation for the Ard Sync II directs users to connect all slave and word clock connections directly to slaving devices rather than using a daisy chain configuration when the Ard Sync II is clock master. Technically this should work, however, Pro Tools audio interfaces don't respond well to this configuration.Connect slave (256x) clock out of Ard Sync II to slave clock in of your first Pro Tools interface. Then connect slave clock out of that interface to your next Pro Tools interface. Continue daisy chaining slave clock out to slave clock in for all Pro Tools audio interfaces.