I seemed to have lost most of my contacts. Any idea why this would happen?

I seemed to have lost most of my contacts. Any idea why this would happen?

I have been adding people to my contacts for the last 12 months since starting Zoho. For some reason, almost none of them are there now - despite me manually putting them in or selecting to add them through their email.
Even people I have emailed several times a day for a year aren't there anymore.

help??