Siri won't allow dictation of new text messages

Since the last update, Siri will no longer allow me to start new voice-dictated text or imessages. If I say "Hey Siri, new message to [contact]" (which I used to do all the time), she now says "I'm sorry, I can't do that."

Doesn't matter what contact I'm trying to send to, doesn't matter how many cell service bars I have (or even if I'm connected to wi-fi).

It works if I am RESPONDING to a message - Siri WILL allow me to dictate a voice response to an incoming message, but I cannot start a brand new message.

Please help.