You didn't specify what model Roku you have. You show a Roku TV as one device, but they are all manufactured by different companies, so we can't suggest who to contact if it's a TV. I use HBO Max all the time on my Ultra 4800 with no issues.
The first step to try when a channel isn't working correctly is to remove the channel, reboot the Roku (don't skip this step, and for a Roku TV this isn't just turning it off and on), then install the channel again.
Thanks for that. That particular TV should have no issues with HBO Max. I suggest first removing the channel as I mentioned previously. If you subscribe to HBO Max through Roku, you won't have an option to remove the channel without first cancelling the subscription. Silly, I know. After you remove the channel, go to Settings/System/Power/System restart and reboot the TV. If that's not the menu location (some TVs have different menu layouts) just unplug the TV from the wall for 30 seconds, then plug it back in and turn it on. Once restarted, install the channel again.