Unable to add Users to collaborate on cloud version

Hi everyone!
Basically I wanted to add a user to collaborate in our organization project. However I am unable to receive the invitation email although I have put the correct email address.

But when I tried to cancel the invitation and try adding my alternate email, I receive the invitation instead. I have tried resending it for several times. Does anyone know how can I fix it? For info, I have been using the same main email to other previous organization and able to collaborate but not this time.

Appreciate anyone who can assist, thank you!