The domain https://fediverse.observer/ redirects to sedo now.
On October 11th these two commits where made to the repo:
this will be my final release, glad to have contributed since 2011 to some fediverse stats, https://fedidb.com/ is a great resource with more interest
this software is no longer developed
Sad to have lost such a great resource.
I just confirmed the problem still exists and messaged them via mastodon about it.
Probably didn’t let them know originally because I didn’t have a mastodon account at the time and already had a good option (fediverse-observer).