I respectfully disagree.
This problem which I'm experiencing is not HBO GO's fault; as you can clearly see in my screenshot, the error was during the FiOS authentication process by which Verizon checks if the account is provisioned for the HBO GO service.
I confirmed this by being able to log in with my Cablevision login without any problems.
I also confirmed this issue with MaxGo (which is essentially the same exact software as HBO GO just rebranded) and on both my computer + my Samsing SmartTV.