I hear your sentiments, @mbursolutions. I can see how the alert message has caused some challenges in your business. Let me provide tips on how we can remove it in QuickBooks Online (QBO), so we can get back to business seamlessly.

If you've already followed the steps suggested by my colleague, MaryJoyD, about deleting and recreating the invoice, we can perform some basic troubleshooting steps to isolate the issue. This way, it removes the accumulated cache that results in errors when using QBO.

First, let's log in to your account through a private window. Please refer to these keyboard shortcuts:

• For Google Chrome browser: Ctrl + Shift + N
• For Mozilla Firefox browser: Ctrl + Shift + P
• For Safari browser: Command + Shift + N

Then, let's check again to see if we're still getting the same alert message. 

If it's resolved, we can go back to your regular browser to clear its cache or use a different supported browser. It might be a temporary issue with QBO and the browser you're currently using.

However, if the error message persists, It's best to reach out to our customer support. They have access to a screen-sharing tool, which can further investigate the cause of the issue. 

When a customer pays an invoice, we'll have to record them to balance your accounts. Otherwise, the invoice stays open and remains unpaid in your reports. Also, we can either record the payment as full or partial, and QBO tracks the remaining balance.

Keep in touch if you have additional concerns about managing invoices. We're right here to back you up. Have a good one.