I've figured out the broken chat!!!!

If both people are logged in, chat works (with some slowness -- up to 45s or so delay before the message is delivered.)

If the other person is NOT logged in, you cannot message them through the chat window. 

BUT -- you can still respond with a message through their blog. You need to navigate to their blog (NOT the sidebar pop-out blog -- you must go to .bdsmlr.com) and hit the little chat icon to send a chat. In the "Send a Private Message to Jennie" (or whomever) you can send them a message and it will get to them.

Not the most useful system for chatting, but it does allow you to respond when they are offline.

The technical:

Chat messages are sent via an HTTP/2 POST to /newmessage2. The newmessage2 handler seems to be broken if it can't send a notification to the receiving part. But the "Send a Private Message" is done via a POST request to /newask (not to be confused with "Ask", which is /newasknew). Both /newask and /newmessage2 go to your chat history, but only /newask is working when the receiver is not online.

Reblog/share this with literally everyone. And you probably want to turn you Online Status to On/Visible until this gets fixed.

I just spend two hours tracing this down. I'm going to bed. Goodnight.