I can imagine the hurdle you've been through trying to fix this, Nancy K.

I'll make it up to you by making sure you'll get the urgent help you need. I see that you've already deleted the bill-payment check and created a credit memo.

Let's start with the balance due that isn't showing up on the vendor's account. When you delete the bill-payment check, QuickBooks will open the bill. 

You can click the Open balance link from the Vendor Information section to see both the open bill and the credit you've created. I've added a sample screenshot below for your visual reference.

For the credit memo, make sure to choose the Credit option from the Enter Bills form. Use the attached screenshot below to see what it looks like.

Since you aren't seeing the credit memo (vendor credit), can you state how the transaction was entered, a screenshot maybe? That way, I can check or locate the credit based on how you record it in QuickBooks.

Meanwhile, do you need to pay again the bill using vendor credit? If so, here's an article that outlined the steps for recording refunds: Record a vendor refund in QuickBooks Desktop.

Please send me an update by commenting below once you have the details and screenshot of the credit memo. I'll keep this post while waiting for your response. Thank you and take care always!