Add new user

Hi. I have problem when I want to add user in admin module. I try to add them by using their email account. After I add them notification pop up and said "1 user has been added. The user is listed on the Pending tab.". After that I check to Pending Tab, but it's empty. I try to contact the user to that they receive email from Zoom? They said not. I try to add another user but it works. 

Can you help me to solve this problem? Because we use Zoom for education purposes and the user are student and also lecturer. Thank you for your help.

Warm Regards,

Raphael Prawira