The recipient's mail server might be blocking the email. Make sure to let them check their spam and junk folders. But if they're still not receiving the email, they can add @intuit IP address to their mail server to allow Inuit email to pass through. Let me show you how.
Send an email to email@example.com. This should trigger the email domain to recognize the @intuit domain as a trusted site. Then try your request again.
Wait at least 5 minutes after requesting a new verification code to see if the email appears in your inbox.
If the email doesn’t appear after 10 minutes, contact your email provider to evaluate security settings for your email profile.
I have this link in case you have other questions about QuickBooks Online (QBO): Help Articles.
Keep in touch if you need anything else. I'll be right here to help.