You have enabled the Split Cost Calculator in Conversion Kit, but the button does not appear on your property page.
Why this happens. The Split Cost Calculator button appears in the booking box only after a guest selects their dates. The calculator divides the total stay price between guests, so it needs a price before it can display.
What to do. Pick a check-in and check-out date on the property page, and the button appears.
Price Alerts and Rate Comparison behave the same way.