Good day,

I understand how crucial it is for you to send invoices. We need to narrow down the issue to resolve this. 

1. What device are you using? Is it the app or your PC?

2. Have you checked if it includes the correct email address of the customer?

3. Have you tried sending it to your personal email? Does it save in the first place?

If you're using the app, kindly uninstall the app. Don't worry, your data are saved and will remain as is once the app is reinstalled. Preferably, try logging into a different device like your PC and try sending and creating a dummy invoice. 

If the invoices bounce when sending, please have it changed to your personal email. There are domains who are blocking emails from Intuit. The receiver can try adding Intuit email address to the safe-sender list for smoother reception.