Back in February, communications between Mbin and Mastodon instances suddenly became one-way, Mbin instances receiving Mastodon updates, but not the opposite.

Pointing that out in a meta thread in my instance, the administrator investigated and found it was an incompatibility introduced in a Mastodon update, and on Github, he proposed a patch to be compliant to Mastodon's expected fields.

And making some quick tests, now that the new Mbin update is out, two-ways compatibility seems to be back.