Hello, @southcountyplumb.
You can delete and recreate your invoices to link the estimates successfully. To delete an invoice, click on the More button beside Customize, then tap on Delete.
If you're getting the same problem, I encourage clearing your browser's cache to start fresh. Sometimes the stored cache of the regular browser you're using may cause unusual experience while working with QuickBooks. For your guide, check out this article: Clear cache and cookies to fix issues when using QuickBooks Online.
Also, read this article for additional reference about converting estimate into an invoice.
Tap on me if you have any other questions by adding a comment below. I'm more than happy to help. Have a good day!