Admin
Revoke a share link
There are two kinds of link: one that expires on its own in 7 days, and a permanent one that never does. A 7-day link cleans itself up; a permanent link — including the one an announce creates — keeps working until someone revokes it, so revoking is its only control and a forgotten one stays live.
From the Admin section, open Shared Links.
Find the link and click Revoke.
Anyone holding the link loses access immediately — for a permanent link this is the only way it ever stops working.