I'm not getting a banner on iOS either, however when I try to send a message it fails with a red exclamation mark in a circle saying "Request failed: service unavailable (503)"

Edit: A few minutes after the message failed to send I got a yellow banner stating that the service was experience interruptions.

However the banner disappeared shortly afterward, so it would have been easy to miss.

Not sure if it's only showing on Android but I had to attempt to send a message first before it showed.

I did see it on iOS

I see the banner in Android.

iOS