I am unable to block off dates for dates that are clearly available. I am not available to with any of my listings. The blocked button is disabled and un-clickable when I highlight a date or a group of dates.
When you block dates the Edit button does not show up in Airbnb web.
You can try in open the calendar page in Airbnb App , to block any dates and check the lower-right corner, you will see a fraction of a green Edit button.
Depending on your device screen size you may not see any remains of the button at all, in this case you will need to switch to a browser version of Airbnb for dates blocking.