Thank you for providing those details and making an effort to fix this issue, Larisa. I understand the significance of receiving accurate notifications for our transactions. I'll share some details and make sure your invoice delivery issue gets resolved.
Since you've already tried some of the troubleshooting steps like clearing the browser's cache and whitelisting Intuit emails, we can perform additional steps to isolate this problem. For the detailed steps for the two methods, feel free to see this article: Test your invoice delivery from QuickBooks Online.
If in any case your customer isn’t receiving the invoices your sending via QuickBooks Online after your successful tests, refer to this link on how to fix them: 3 solutions for when customers aren't receiving your emails.
If you need any additional assistance with sending invoices in QBO, please leave a comment below. I'm always available to assist. Stay safe, and enjoy the rest of your day, Larisa.
