The car tells me I have a new message, displays who it is from, and then shows a blank box for the message.
Yes - if the car is moving - your only options are to "Read" (i.e. Pamela will read it to you), or "Ignore", which will close out the dialog box.
Aha! That makes a lot of sense. Thank you - my blank text messages stymied me, too. My "technology specialist" was not terribly thorough when running me through the features, and I figured I would read the manual later - but haven't gotten around to it yet. I'm still not used to giving voice commands to my car!
I only very occasionally see the read button - perhaps after the system reboots, which it does occasionally. It is usually grayed out. But holding down the Siri button and saying "read new message" works just fine. This is with an iPhone 6S, latest iOS.
Apparently I can't dictate a text reply, though this is supposed to be a feature. When I try, I'm told that "this function is not available on the connected phone." Is there some trick to this? I just sort of assume that an iPhone 6 is going to be up on the latest tech, but Apple and Toyota have never particularly played well together.