Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
After some struggle (removing apps, restarting Roku, adding apps back), I'm able to play HBO Max on my (2012 Samsung) smart tv through the Roku Streaming Stick (1 yr old) but am unable to play the channel on my (2 mo old Android) phone using the Roku app. Max doesn't show up as an option at the home screen in the phone app as it does for other subscriptions. When I locate it using the search function it brings me to a screen prompting me to "Launch". Clicking launches HBO Max on my tv with no prompt asking "where do you want to watch?" with mobile as an option as occurs for any other channel. I could get the app not recognizing my old tv (Netflix no longer supported) but why would there be an issue with a new Android and why is it casting to my tv for this app only?
HBO Max subscriptions are not available through the Roku Channel (nor is accessing HBO Max-specific content).
The Roku app (Android in your case) can remotely control your Roku - including launching apps on the Roku, and controlling your Roku (and Roku apps) using the phone as a remote; it can also play content on your phone that it has access to through the Roku Channel.
There will be no option for "where do you want to watch?" unless the content is available through the Roku Channel - which HBO Max is not.