Let's make sure to fix the Sales Order fulfillment worksheet error that you're getting, Nathan at Kasten.

Thank you for providing a screenshot! The Sales Order Fulfillment Worksheet helps you manage and fulfill your sales order by providing you with a single place to gain insight and access to all aspects of the process with better and easier workflow.

We can perform the Verify and Rebuild tool to identify the most commonly known data issues and resolves them after we're able to determine the cause. 

To verify data:

1. Choose Window then Close All.
2. Verify Data. Choose File then Utilities. Select Verify Data.

To rebuild data:

1. Choose File, Utilities then Rebuild Data.
2. The Rebuild Data utility starts as soon as the backup is finished.
3. Click OK when you get the message "Rebuild has completed".

Moreover, you may be experiencing other errors when using QuickBooks Desktop, you can check out some of the solutions found in this article: Fix Data Damage On Your QuickBooks Desktop Company File. 

Let me know if you have any other concerns with the fulfillment worksheet or if you have additional questions about QuickBooks. I'll always be right here to help anytime.

Unfortunately verify and rebuilding didn't help. What is the next step?

I'm here to share additional steps to fix the issue, Nathan at Kasten.

Making sure your QuickBooks Desktop software is up to date should be our first step. This guarantees you have the most recent features and fixes.

To be sure, did you also receive the same trouble creating invoice for other sales order while using the Sales Order Fulfillment Worksheet? If not, you can open the affected sales order and ensure all the required details are filled out. 

If so, you can download and install QuickBooks Tool Hub to check for unusual errors and immediately fix them. 

Here's how:

1. Close QuickBooks.
2. Download the most recent version (1.6.0.3) of the QuickBooks Tool Hub. 
3. Open the file you downloaded (QuickBooksToolHub.exe).
4. Follow the on-screen steps to install and agree to the terms and conditions.
5. When the install finishes, double-click the icon on your Windows desktop to open the tool hub.
6. Select Program Problems.
7. Click Run Quick Fix my File.

For your reference, visit this link for the complete information on the process: Fix common problems and errors with the QuickBooks Desktop Tool Hub.

If the issue persists, I recommend contacting our QuickBooks Desktop Support. They have the resources to perform a screen sharing to further assist you in fixing the problem.

I'm including this article for a step-by-step procedure to create an invoice coming from a sales order for future reference: Create an invoice in QuickBooks Desktop.

Feel free to post again if you need anything else in QuickBooks. Have a great day.

Quikbooks is up to date and QuickBooks Tool Hub did not find any errors. 

Any other ideas to help?

I am leery about contacting customer support as were not able to help with past issues and wasted tons of time chatting and zero call backs from four requests. 

Thanks for getting back with the Community, Nathan at Kasten. I appreciate you performing MariaSoledadG and Giovann_G's recommended troubleshooting steps.
 

Since you're still encountering the message, I'd recommend continuing to get in touch with our Customer Care team. They'll be able to pull up your account in a secure environment, conduct further research with you, and create an investigation ticket if necessary. They're also able to initiate screen viewing sessions if you're alright with doing one. This can help you and them to identify what the cause of your message is.
 

They can be reached while you're using QuickBooks.
 

Here's how:

1. In your top menu bar, go to Help, then QuickBooks Desktop Help.
   
   
    
2. Click Contact Us.
   
   
    
3. Enter a brief description of the issue in our Ask a question (or tell us what's wrong) field, then hit Continue.
   
   
    
4. Select We’ll contact you for a callback or Message Us to start an instant messaging session.

Be sure to review their support hour so you'll know when agents are available.
 

I'll be here to help if there's any additional questions. Have a wonderful day!