I'm here to share some information about invoices that we're not sent from your QuickBooks Online (QBO) account, @little-miss-orch.
Our team is aware of the issue and is working to create a solution that will resolve it. We're now taking steps to address this problem. Please know that this is a top priority for us, and it will remain so until it is entirely fixed.
In the meantime, you can save your invoice as a PDF and send it via email through your business or other email address.
Go to the Sales menu and then proceed to the Invoices tab.
Find the invoice and click on the dropdown under the Action column.
Choose Print and then click on the Download icon beside the Print icon on the page that appears.
Follow the prompts to save the PDF file.
Once done, attach this file to the email that you'll be sending them outside QBO.
Refer to this article for more information about creating and sending the invoice: Create invoices in QuickBooks Online. This will guide you on how to review open invoices and notify customers about upcoming invoice due dates.