Can't sync Calendar and Contacts with Android mobile

Can't sync Calendar and Contacts with Android mobile

Hi. I want to sync Zoho Calendar and Contacts with my Android phone. I followed the instructions here.

My phone is a Samsung Galaxy S2 Advance with Android 2.3.6.

When I first set up the account all the data was copied to the phone correctly. But now the updates are very unreliable in both directions. For example, when I add events to my Calendar at the Zoho website they do not appear on the phone.

I tell the phone manually when to perform a sync.There is no error message from the phone. It just carries out the sync but no new data is displayed.

I deleted the account and set it up again, but it was no different.

Can you please help. Bob B.