The sales order feature is available for QuickBooks Online (QBO) Plus and Advance subscription, userinfo18.

If you're using a lower version of QBO plans such as Simple Start and Essentials this feature is unavailable. I recommend upgrading your QBO Online Plus or Advance.

If you are using these versions, let's begin by troubleshooting. First, add Intuit as a trusted site. Then, clear your browser's cached data and any cookies associated with Intuit.

Additionally, your computer's internet speed and web browser version can affect the software's performance. To ensure a smooth experience, make sure you are using the latest version of your browser and that you have a stable internet connection.

For a comprehensive guide on using Sales Orders in QuickBooks Online, including how they work with different subscription levels, check out this article: Create and manage sales orders in QuickBooks Online.

You may also check this article for your future reference about sending invoices: Send an invoice to a customer.

If you still have further queries, reach us here in the community support.

I use Plus, cleared cookies, use new invoice version, have the newest Chrome version. What's next? It still doesn't work.

Good morning, @userinfo18. 

Thanks coming back and letting us know that you have QuickBooks Plus and that those troubleshooting steps. 

If you aren't able to see the Sales orders option in the +New or Sales function tabs/buttons, then I recommend contacting our Customer Support Team for further assistance. They'll be able to review your account with you to see why this is happening. Here's how: 

1. Go to the Help icon in the top right-hand corner. 
2. Press the Contact Us button. 
3. Enter your question and hit Let's talk. 
4. Scroll down and to Get a callback. 

Keep us updated on how the call goes. I'm only a post away if you need me. Have a great day!