Cannot Add User who has a Zoho Account to my Business Portal

I have been experimenting with the free 3 user Zoho Account. Was ready to sign up and start migrating all our company users to a paid account.

So first I tried...

Add a new user directly

So I generated an invite to one of the guys who already has Zoho Account.

He logs in with the name@mydomain.com / password that I assigned.

And now it wants him to create a Zoho ID. No option to let him use his existing Zoho ID ??

Stuck.

Then I tried it the other way...

I sent the invite to his existing Name@zoho.com email address.

He Clicks on the Accept link, and it just takes him to his main Zoho Mail. Nothing related to joining the organization...

Stuck.

Wasted about an hour on this and very frustrated that it can be this difficult.

Please help.

Daraius