Please ask your clients to check their junk or spam folders, as the invoice may have been delivered there. If they still cannot find the email, you can reset your email setup by following these steps:
Click the Gear icon and select Account and Settings.
Select the Company tab, then click the Contact info section.
Clear the Company email field and re-enter the desired address, even if it is already displayed correctly. Ensure there are no extra spaces or characters before, within, or after the address.
Click Save, then Done.
Next, send yourself a test transaction. If the issue persists, you may need to use an email address with a different domain.