Bridge & your devices · Collab Sync
What does “Pair another Mac running Storage Studio first” mean in Collab Sync?
Short answer: Collab Sync needs a Mac already paired through Bridge, and there isn't one yet. Pair another Mac running Storage Studio in the Devices tab, then add your synced folder.
Collab Sync can only mirror a folder with a Mac you've already paired through Bridge, and none is paired yet. Pair the two Macs first, then come back and add a synced folder.
The other Mac must be running Storage Studio — a Windows PC with the Bridge app can't be chosen here.