The Billing & Subscription tab didn't go anywhere, Nonies. You can still locate them in QuickBooks Online. I've got some steps to resolve this.
Before proceeding, verify if you're logged in as Master Admin or Company Admin. If so, I suggest following these steps:
Go to the Gear icon.
Select Account and settings.
Choose Billing & Subscription tab.
From there, you're able to locate your subscription(s).
For your visual reference, I've attached some screenshots below.
However, if the tab is still missing, let's access your account via a private window to determine if this a browser-related issue.
Here are the keyboard shortcuts:
Safari: Command + Shift + N
Google Chrome: CTRL + Shift + N
Mozilla Firefox or Microsoft Edge: CTRL + Shift + P
After signing in, perform the steps above. If it works, I suggest clearing the browser's cache. This improves the performance of the program. You can also use compatible browsers. They will provide you the best and most secure experience with QuickBooks.