I had to post 4 1/2 months ago for this same issue. It happens on and off every now and then but it has been ongoing for about the last week. I’ve had issues with the chat portion of the iPhone and iPad app. When I click messages, they won’t open. Sometimes, if they open, I can’t see anything and it gets stuck at the loading screen. When I initiate a new message, it will open the chat with the user but nothing I typed appears. I’m also unable to accept new messages. Also, it shows I have unread messages when I actually have none. Lastly, when replying, none of my messages go through. Often, the chat feature will work on my iPad and then not the iPhone or vice versa. Right now, neither is working.

To fix, I've uninstalled and reinstalled the app a billion times to no avail. I logged on via the web browser today and experienced no issues.