Syncronization error

Hi, my phone (HTC with Android 4.4) has stop to sync with Zoho active sync.
The last sync of calendar is 18/02/2015 @ 17:36
The last sync of contacts is 06/02/2015 @ 00:37
I made no changes in settings.
I'm using msync.zoho.com.
I cannot remove and add again the exchange profile because I loose all contact that I add from 06-02-2015 to today.
Can you check why my attempt to sync fails?
Please answer me ASAP.