Gmail Gadget Login

Gmail Gadget Login

Hello, I can't seem to activate the Zoho CRM Gadget for Gmail (using Chrome). When I click on a name in the gadget to link an email to a contact, I receive this message:
Looks like you are logging into Zoho from Google for the first time. We'll open a new window to associate your Zoho ID with google.

I am then taken to a pop up window where I'm asked for my username, but when I enter the username it tells me that the requested username has already been taken.  How can I link my Gmail and my Zoho CRM accounts?

Thank you