@Marcia464. I was able to enquire on some dates in April for both listings, so appears bookable. Could just be slow, as we are finding here.
Private browsing simply means make sure you log out of ABNB completely as a host and close the tab then open a fresh tab before searching on ABNB. Firefox is a good browser thats supposed to leave less of an internet search trail.
If you really want to know what UD means then suggest you message Superhost support; they seem to answer the easy questions pretty quickly these days. Then let us know 😉