Update: I fixed it. You can all find me on Mastodon again.
I knew this was going to happen one day. I tried to upgrade my own Mastodon server, which runs on a raspberry pi, here at home. I followed all steps, and now it doesn’t work anymore. The problem is, of course, that I do follow the steps, but I don’t really know what I am doing. So now, no new messages arrive, and as far as I know, messages I write are not sent. I will try to fix it in the coming days.