tcywiki was created today, so you've probably never received a notification there. If you go to https://tcy.wikipedia.org/wiki/Special:Notifications, you should expect to see something that lets you view unread notifications from other wikis still (like when you go to Special:Notifications on wikis where you have historical notifications but no unread ones), but instead it just shows "You have no notifications" and no UI whatsoever.
Reported by @Reedy on IRC while tcywiki was being set up.