Thank you for posting here in the Community, @userinfo126.
Let's perform some troubleshooting steps so you can access the Billing and Subscription menu.
It's possible that the browser you're using had a data issue that's why you've got an error when accessing some of the pages in your QuickBooks Online (QBO). To verify, let's try logging in to your QBO account using a private browser. To do so, press this shortcut key on your keyboard:
Google Chrome: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Safari: Command + Option + P
Once logged in, go back and try to access the Billing and Subscription menu again to double-check. If this works, it means that you need to clear the browser's cache so the system can start fresh. If you get the same result while using a private browser, I recommend switching to a different one.