Thanks for letting us know about the playback issue that you are experiencing.
We recommend starting here to troubleshoot channel issues: Follow these steps in order:
1.Navigate to the channel tile on the Roku home screen, press the * key on your remote, and choose 'Remove channel'.
2.Next, restart your device from Settings>System>System restart. (For Roku TV Settings>System>Power>System restart)
3.Once your player/TV starts up again, go to 'Streaming Channels' on the Home screen, and add the channel back once more.
If that still doesn't clear up the issue you're experiencing, we recommend contacting the channel provider directly to follow up for more help. They’ll be able to best assist with any issues that are occurring within their channel.
You can reach HBO Max support here: https://help.hbomax.com/