I see that someone posted there just 11 hours ago, so it may be temporary.
I was also able to post just now, but I guess mbin masks quite well the case of the host node being offline because it posted fine, probably just to a fedia.io cache of dabradio.
Regarding my user not being found, that looks like an MBin bug with underscores in usernames. I have a bot with an underscore in the name and it does the same thing. Hmm, I’ll raise it on the issue tracker if it hasn’t been already.
Edit: https://github.com/MbinOrg/mbin/issues/1748
I was able to get an Mbin dev server set up and can confirm it’s nothing on our end:
I couldn’t tell you what’s actually going wrong in Mbin as the server isn’t actually processing the requested object.