"Google's Task List" is empty in the "Apps & Add-ons" section of the Setup

"Google's Task List" is empty in the "Apps & Add-ons" section of the Setup

Hello,

I had no problem to make the link between our Google Apps domain and our Zoho CRM, all is working fine, Except for Tasks.

I can't choose a task list in the setup to make te link for this last option. I attached a printscreen to illustrate the case. I tried to create another tasklist, but nothing changed. 

Can you help me what to fix that ?
Zoho Plan : Professional Edition
Active Users : 2
Paid Users : 2
Zoho Mail Add-on : 1
Zoho CRM Mobile Edition : 1
Thank you very much :)