"personal conversation requiring approval"

[lactsl]

I received an email from my board today with the following info:

X has posted a message in a personal conversation requiring approval, X

​When I click 'Go to message' I am told:

Sorry, there is a problem

We could not locate the item you are trying to view.

I have received another similar email today, this time when someone sent a PM. I have never seen this before. What's going on?