To summarize, I have multiple payments to a vendor that put that vendor well over the 1099 reporting threshold. Payments associated with "Account A" appear in the 1099 NEC column. Payments associated with "Account B" do not. Both accounts are expense accounts with the same type and detail type. All payments were made from the same checking account and with the same "payment method". How is it possible that these payments are being treated differently when it comes to the 1099 NEC column? How do I fix it? It seems like there should be a way to fix these accounts so that they function the same way.
Thanks for getting back here, @fish6. I want to ensure this will be taken care of.
I can see that you did everything you could. To further help you with this, let's verify that all of the accounts used for 1099 are assigned to the box on the form. You'll see this on the Prepare 1099s page. To include amounts on 1099, the account must be assigned to a 1099 box. Check this screenshot for a visual guide:

If you noticed that a vendor was not included in Step 4 of Prepare 1099s, simply select the funnel icon located at the upper left part of the page. Then, in the 1099 contractors that meet the threshold section change Type of contractors to 1099 contractors below the threshold and click Apply. This will display the vendors with insufficient payment amounts to require 1099.
You can also select the amounts to generate a report showing each transaction. From there, check the Account column to see which account is used for each transaction.
For more details about the process, please proceed to the Accounts are not mapped to 1099 boxes section of this article: Common Causes for Incorrect Amounts on 1099s.
However, if verified that all accounts are assigned to the 1099 box and you still can't see the payments, I highly recommend reaching out to our Payroll support team. They use specific tools to pull up your account and investigate the root cause of the issue. You can also request a screen-share session so they can review your set up.
I've also added this helpful resource that you can access to have a guide in case you need to make corrections to 1099-NEC or 1099-MISC forms after you e-filed them: Correct or change 1099s in QuickBooks.
I'm always around the Community if you have any other concerns about managing your Form 1099-NEC. Don't hesitate to post again here. Have a good one and keep safe.