They mentioned that were blocking all ‘bot’ user-agent strings, which unintentionally also blocked /kbin bot.
The issue is finally landed to the devs, thinking there was no such block (but there was). Anyhow, it’s now been resolved. Federation should finally work again.
See also: https://lemmy.world/comment/1082149
@Countmacula if was indeed causing a lot of frustration, questions and on the server side: also technical issues with the message queue etc.