Continuing the discussion from Forum rules update (March, 2021):
Welcome back, @gandalf78! Normally that page is shown when the URL is not valid or the message has been deleted. If you’ve bookmarked messages from the previous platform, the URL likely won’t work. But you should be able to find your messages using at https://talk.collegeconfidential.com/my/messages. You can also get there by selecting your avatar in the top bar:
(Ignore the red 3.)
Unfortunately the way messages were imported means they all have similar titles:
(Your numbers will vary.)
But you can use search to find old messages:
If you continue to have problems finding your messages, let me know and I’ll see if I can help out.