I have an iPhone having the same issue.  I was able to get a keypad displayed by tapping the bottom-center of the screen.  Still haven’t found access to “settings” though.

Hi,

Thanks for reaching out! Could you confirm if you're using a paid RingCentral account or a free one? The dial pad may not appear for free accounts or if calling features are not enabled for your user.

Also, please check your app permissions (especially for microphone and phone access) and let us know if you're still experiencing the issue. Looking forward to your response!