Sync Calendar greyed out in Outlook toolbar

Sync Calendar greyed out in Outlook toolbar

I'm currently trialling Zoho CRM for my business as a replacement for Netsuite, which is much more expensive and nowhere near as customisable as Zoho. Well done on a fantastic product for small businesses.

I've enabled the Outlook Plugin 15 day trial and installed the plugin. I can login into Zoho CRM from the Outlook toolbar and I can add a Case to Zoho contacts, but Sync Contacts, Sync Tasks and Sync Calendar are greyed out so I can't use them. What am I doing wrong.