If deactivating the Power Saving setting (or if you do not have that option), it's possible that there is an issue with the channel and I'd recommend reaching out to HBO Max directly to report the issue and request additional support. Many channels on the Roku platform are developed and maintained by the channel provider directly, and they'll be able to best assist. If other channels are working correctly, and you only experience this issue on the HBO Max channel (app), that is likely an indication that the issue lies within that particular channel. In these cases, the channel provider will need to investigate the issue in order to help resolve it.
You can reach them here: https://help.hbomax.com/us/ContactUs
Please keep us posted what you find out.
Roku Community Moderator