I think it have to do with the root then. I use Phh SuperUser. SuperSU didn't work well with the earlier version of Magisk so I switched to Phh SuperUser. Also you must be SYSTEMLESS rooted. Might be why you got problems.
How I did was first download it from Play store, go in to SuperSU and checked that I wanted to remove it and it's features. Rebooted the phone, opened Phh SuperUser so the phone know it's the one that is suppose to be the grandmaster.
In Magisk Manager download Phh SuperSu addon for Magisk after you installed Phh SuperUser from Play Store
Then open Magisk Manager and SuperUser should ask if you want to give it Root Access.
Then reenable Magisk Hide and reboot your phone.
https://forum.xda-developers.com/apps/magisk/official-magisk-v7-universal-systemless-t3473445
https://forum.xda-developers.com/apps/magisk/magisk-phh-s-superuser-android-pay-t3435921
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Well HBO have this odd protection (Android SafetyNet) because they probably think people will pirate their shows from their phone......
The reason probably why this is protected against root is you can't cheat more "pay" stuff in.