why i get this messages ( we couldn't send your invoice)

There are several factors we can check to determine why your invoice was not sent, @customer12_2.

The error message you encountered in QuickBooks Online (QBO) indicates that there was a delivery problem with the email. Even if QBO sends the email successfully, the recipient's server may reject it or mark it as spam due to strict security settings or flagged email addresses.

If the issue persists after checking the recipient’s spam folder, I recommend deleting and recreating the invoice to see if the problem is related to the browser you are using. Additionally, try sending a test invoice to another email address using a private browsing window, and ensure that your email settings and app data for mobile apps are correct.

Here’s how to open a private browsing window:

• Press Ctrl + Shift + N (Google Chrome).
• Ctrl + Shift + P (Firefox).
• Control + Option + P (Safari).
• Ctrl + Shift + P (Microsoft Edge)

Refer to this article to find out why your customers may not be receiving invoice emails: Troubleshoot if customers aren't receiving emails from QuickBooks Online.

Feel free to leave a comment here if you need more help with QuickBooks.