I appreciate the steps you've performed so you can remove the company file from your list, @NicoleS1.
As my colleague discussed above, you'll need to reach out to the Master Admin of the QBO account to detach the company from your list. The Master Admin has general access to remove and invite users to specific company files.
Also, from your statement that the company subscription has lapsed. Does this mean that the company has expired or cancelled? If so, the program will delete this after a year. After that period, you'll no longer see the company on your list. For your reference, see this article: What happens to my QuickBooks Online data after I cancel?
Then, for further assistance and actions you need to take, I highly recommend reaching out to our support team. I know that you've already contacted them, however, they are the ones who can access your account in a private place. This way, they can check that test company file and help you remove that on your lists.
I've also added this article so you'll have a guide in case you need to add users for your accounting firm: Add and manage your accounting team in QuickBooks Online Accountant.
Feel free to get back to me if you have further questions about removing a company from your lists. I'm just a post away to help you. Keep safe.
