Rocket Chat app tells me 'New user registration is currently disabled'.

I'm trying to get the Rocket Chat app to work on Android via the instructions posted by Seeking Alpha, https://feedback.seekingalpha.com/en/knowledge-bases/2/articles/184501-how-do-i-access-rocket-chat-via-the-app.  I do everything as asked and Rocket Chat gives me the same results every time 'New user registration is currently disabled'.

Can someone help me out?