Add a second user to my free CRM-Account

Hi there!
I have invited my employee to join zoho in order to work with the CRM. However, she is always asked, if she wants to join our companies account or open a new account. When she's choosing "joining the company account" there is a hint to contact the support.
That's what we have done, but probably you already know what's the issue and can help ;=)

Thanks a lot
Beat