I pay for HBO Max through Roku. It works fine on my TVs. HOWEVER, I cannot figure out how to watch it on my android phone. I've read every help topic and article. HBO shows up as a paid subscription in the android app but you cant access HBO max there. It was suggested (by Roku) to use the Roku logon info when signing into the HBO Max app but that doesnt work either. Someone please help meeeeeeeee
Although I do not have HBO Max, I believe it is similar to all other subscriptions purchased through/paid through Roku. Namely, you need to access the subscription through your Roku device only.
If you paid for your subscription directly through the provider (HBO Max), then you would be able to watch your subscription on any device (Roku, phone, tablet, etc).
Now some subscriptions can be watched from your phone or computer "through" the Roku Channel after you sign in but not sure if HBO Max is one of those.
Here is Roku support article on it. Post back if I missed your question or you need more help.
https://support.roku.com/article/1500008104062