Roku does not create the channel apps, the channels (in this case HBO) do. Roku just provides the platform on which they run. Each channel app is encoded with the countries/regions in which the channel owner permits it to operate.
It sounds like HBO has not included your area in the coding of their HBO Max Roku app, either deliberately or as an oversight. You need to take your complaint to them. http://help.hbomax.com/
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X