What can I do ,'Billing and subscriptions' routinely does not show up under accounts and settings; quite frustrating when one wants to access the monthly invoice ?

Hi there, @matobovet-office.

Performance issues in QuickBooks Online are resolved by doing basic troubleshooting steps. Let's start, logging in to a private window and access your account there this way we will know if it's the browser causing the error.
 
Here are the keyboard shortcuts:
 

• Google Chrome: press Ctrl + Shift + N.
• Mozilla Firefox: press Ctrl + Shift + P.
• Internet Explorer: press Ctrl + Shift + P.
• Safari: press Command + Shift + N.

If it work's fine using a private window, proceed to clear your browser's cache. Clearing cache and cookies will also help improve the browser's performance. 

If you still have the same error after following the recommended steps, use other supported browsers in QuickBooks Online.

If the unexpected behavior persists, I suggest reaching out to our Customer Support Team. A specialist will look up your account and can investigate this issue further, please click this link: Contact the QuickBooks Online Customer Support team.

I'll be here if you have more questions about QuickBooks. Wish you all the best!