I'm having the same issue today and yesterday.
I am a co-host of 2 properties. I can view details and messages from most guest via my IOS app but for the 2 guests that are checking in and checking out today I am getting "Error You do not have permission to access this resource."
This is such a terrible user experience for both host and guest. I've had new guests waiting outside the building for 30 minutes because I didn't get their messages. My cleaning was delayed by an hour because I didn't know the old guest had left already.
The primary host can see all the messages.