When pasting the webinar attendee link in an android mobile browser, users cannot open the RingCentral mobile app to join a webinar.
Android users are opening the webinar link in a mobile browser with desktop mode enabled.
You can choose to join the webinar from the browser when prompted. Alternatively, you can simply tap on the attendee link instead of pasting it in the browser. This would automatically open the RingCentral mobile app if you have it installed on your phone. Visit Joining a webinar via mobile for more information.