"This calendar is already connected to a different room"
This message means the Airbnb calendar link you just pasted is already attached to a different room on this property. Each room needs its own calendar link from Airbnb; pasting the same link twice, for two different rooms, is what triggers this.
How to fix it
Check the other rooms on this property's listing pages; the link is very likely already connected to one of them.
Go back to Airbnb and get the correct calendar link for the specific room you are trying to connect here; each room has its own link even though the property is the same.
Can two rooms ever legitimately share one calendar?
No. If two rooms are bookable separately, they each need their own Airbnb calendar link; a shared link means Airbnb itself only sees them as one bookable unit.
Message us on WhatsApp with your property name, the exact error or a screenshot, and which step you were on. We will try to reproduce it and reply the same business day.