I guess it just doesn't like you? :)
2015-02-15 10:20:41 LOG_INFO: [social.umeahackerspace.se:2577.2779a26a POST /main/ostatusgroup] HTTPClient: HTTP POST http:/
/quitter.se/main/salmon/group/1025 - 200 OK

I subscribe by going the the group's page on # and clicking the "Join" button, fill in my webfinger ID and get sent to my home instance. Nothing fancy.