Epic will turn the master server for UT2004 off on January 24th 2023.

Source: https://www.epicgames.com/site/en-US/news/epic-is-turning-off-online-services-and-servers-for-some-older-games

That means that the list of servers in the server tab will no longer be available.

Unfortunately, Epic has also decided to remove UT2004 from the Steam shop.

After January 24th, you will still be able to directly connect to any server if you know its IP, or to connect to any server that you have added to your favorites.

Here is CEONSS's new IP: 194.26.183.119:7788

Make sure to add all the servers you like to your favorites before that date!