You're not missing anything, Mikey007. Good job, though, for doing the steps my colleague provided.

Another step that you can do to fix it is to repair QuickBooks. This fixes program-related issues. I'm here to guide you. 

Before doing it, let's create a backup copy of your company file to avoid data loss. 

Once done, let's go ahead and repair the software. Here's how:

1. Click Start or the Windows icon, and select Control Panel. (In Windows 8/8.1: From the Start menu, open Search, and type Control Panel. From the results, select Control Panel.)
2. Go to Programs and Features, then select Uninstall a program. If you don't see these options, go to Programs, then select Program Features.
3. Select QuickBooks in the list of programs, then click Uninstall/Change.
4. Click Continue, then Next.
5. Select Repair, then Next. Wait for the repair to complete.
6. Click Finish, then restart your computer if prompted.

After repairing QuickBooks, recreate the purchase order from the estimate, then check if you can already see the customer name.

I'll include screenshots for better guidance.

A purchase order is part of the Accounts Payable (A/P) workflow. I'll share the article about it, so you'll learn more about how it works.

If any question arises, you can tag me. I'll personally reply to you as soon as I can.