Cant add user - says Zoho CRM ID already exists

Hi,

I have just set up a free Zoho CRM account and loaded all my data from Salesforce.

I then tried to add a business colleague as a second user but when I use his email address as his Zoho Id it tells me this has already been used.

This is because my colleague was also testing Zoho and so has created an account.

He has finished testing and I know want to add him as a user in the Zoho CRM instance I have created.

Where can I go from here ?

Thanks for you help,

David