It has been fixed. Unfortunately for those who may be stumbling across this page with this same problem in the future, the tried and true “rage quit and try again tomorrow!” strategy solved this for me. My best guess is that Navigraph takes a few hours to update subscription status, which is why I had the issue. I connot know with 100% certainty as I successfully booted the program this morning with no issues or troubleshooting required.
However, I see another post this that seems to be a solution to this issue here: "Navigraph Hub cannot be closed" Message - #2 by RotaryLounge855 if anyone still needs help.