The Online Bill Pay feature of QuickBooks Online is powered by Bill.com. Currently, they are having system maintenance which is why we're temporarily unable to make a payment. You'll want to check and subscribe to the Bill.com status page for updates.
The estimated downtime is 4 hours. Rest assured that you'll be able to pay your bills after this.
Thank you for your patience and understanding.
I've added these articles to learn more about this feature: