I just tested on a Galaxy S9 with Chrome and could see the button, click on it and see the "Start a conversation?" message.
Can you tell us:
* What browser you're using?
* If there's any adblocking or other privacy add-ons on your phone?
* Any other details about the testing environment?
I don't know of anything we can do to diagnose this as we can't recreate it and it seems like something specific to your phone. If you are able to test with someone else's Galaxy S9, that would be great as well.
Thanks,
Alex