Thanks for visiting here,
As of today, November 28, 2020, there is no planned maintenance in QuickBooks Online. You can check the alert on your dashboard for the upcoming maintenance date and time.
During a system outage, you’ll see an Out of Service page at https://qbo.intuit.com. Once the service is restored, the Out of Service page will be replaced by the regular QuickBooks Online login page.
You can also visit this link to see the status here: QuickBooks Status.
Please let me know if there's anything else you need or other concerns with QuickBooks Online. I'll be around to help you out again. Have a good day!