Welcome to the Community, @ngorzkiCEA.

Let me help and provide information about the missing attachments in sending an email later in QuickBooks Desktop (QBDT).

To start, I recommend verifying if the invoice has successfully attached the file. Also, ensure that the attachment meets the required file size for it to appear on the send form page.

Once you have verified all the information, you can proceed with verifying and rebuilding your data.

For future reference, you can check this article to guide you through the process of customer payments for invoices and in-person sales: Take and process payments in QuickBooks Desktop.

Please don't hesitate to leave a comment below, if you have further questions about the missing attachments or other QBDT-related concerns. We're always happy to help you out.