Hello there, @hello84.
It seems like the message you've revived is the one indicated in your client's invoices. You can check it by going to the Invoices menu or via the email's Spam or Junk section.
- Go to the Invoices menu.
- Locate the invoice.
- Under Action column drop-down arrow, select View.
- Scroll-down the page and see the message under the View details button.
For the second option, log into your email. Go to the Spam section as shown in the screenshot below.
After sending an invoice in QBSE, you can refer to this article what are the next tasks you can perform: Send an invoice. It contains set of activities for you and your recipient, such as marking the invoice as paid and receiving payments online.
In case you're referring to something else, let us know by leaving a comment below. This will help us go directly to your issue and provide an accurate resolution
Please let me know if you have other concerns. I'm just around to help.