Trouble adding client user to project

Trouble adding client user to project

Hello.  I have added a client user and opened a specific project to them.  I have also added individuals from the client to the project.  When the client has attempted to use the zoho email address to report an issue to the project the client has received a bounce back that their email address is not registered.  

Also, I was initally unable to import users from the CRM.  Once I was able to do that the screen would continually freeze and not allow me to import.  I eventually added the client manually to the project.  I am listed as an Administrator.  Any help would be appreciated.

Thank you.

-Jeff