There are different reasons that could be causing this. You can find them below:
1. Email address: Confirm with the onboardee if her/his email address is the same as the one added to the profile. If not, correct it and resend the invitation. Following the invitation all the emails that should be send will go to the right email address.
2. SPAM folder: It is possible that the email landed in the spam folder. In case the email is there, ask the onboardee to make sure to mark our email address ([email protected]) as safe and it should not occur anymore in the future.
3. More than one onboardee, using the company email is experiencing the same: In that case, please check with your IT colleagues if our domain is being blocked. In case positive, after unblocking it, the issue should not occur anymore.