Twitter has made a change to its interface, which means that one must now be logged in to the service to use Twitter’s search function.
Previously, anyone could use the search function on Twitter’s website. Now, the search box has disappeared for those who do not have an account on the service and have not logged in. If you go to Twitter.com without being logged in, a general feed appears that seems to be tailored to the country you are visiting the service from. However, if you click on a tweet in the feed, the search box appears again, but if you try to search for something, you are prompted to log in to the service.
Why Twitter has removed public search functionality is something that Twitter, or the service’s owner Elon Musk, has not yet commented on. However, I assume that it has to do with Twitter wanting more logged-in users, something that this change may lead to.