Chat on iPhone too small

New to using the Chat feature. Dropped the code onto a test webpage on server and it works fine on Desktop. The Settings of Chat previews shows with normal preview width for Mobile.

But the view on the actual webpage on an iPhone doesn’t render very well. It is unusable. Too small.

Is anyone using it successfully with a mobile device?
I must be missing something.

I’m afraid I can’t reproduce this on my iPhone SE2.
This might be a combination of issues e.g. using desktop versions.