I keep receiving the message 'We weren't able to schedule this payment' when attempting to a schedule a bill payment. Attempted different browsers, including incognito.

Experiencing common issues with scheduling bill payments can be challenging, Joseph.  

I will make sure you receive the appropriate assistance to resolve this issue.

I also recognize your effort in performing some troubleshooting steps to resolve the error message. Since the problem continues, it's best to contact payments support. They can offer information regarding the error and investigate by accessing your account.

Here's how: 

1. In your QBO account, select Help (?). 
2. Choose the Search tab.
3. Click Contact Us.  
4. Type your concern. Then click Continue. 
5. You can choose Callback, Appointment, or Chat to connect with us. 
6. Kindly fill out the provided fields such as your First name, Last name, Email address, and Phone number. 
7. Depending on what you choose as your way to connect with us, click Callback, Schedule an appointment, or Chat. 

Check this article which provides further information regarding the online bill pay feature in QuickBooks Online: Learn about QuickBooks Bill Pay for QuickBooks Online.

Moreover, you can generate reports to see a comprehensive view of your vendor bills or monitor the financial condition of your business.

Share your questions in the Community space again if you require further information regarding bill transactions. I am here to assist you.

@joseph-szakaly-g 

Another option, you can sign up for a free Melio account to sync with QBO to pay bills. You can also get a $100 cashback to pay the first bill.

https://quickbooks.intuit.com/learn-support/en-us/reports-and-accounting/has-anyone-been-able-to-set-up-the-new-online-bill-pay-since/00/1378612