Can't get kbin.social and my home Lemmy instance to talk to each other - can anyone help?

I'm having trouble getting my home Lemmy instance (lemmy.federate.cc) to play nice with Kbin and I was hoping you all might be able to shed some insight.

I'm able to find and subscribe to Kbin communities from the Lemmy side, but no posts ever come through.

On the Kbin side, it doesn't seem to know my instance exists, and if I search for communities (e.g., mixology@lemmy.federate.cc), there are no results.

Does anyone have any ideas? Thank you!