After the sign up process, you will receive confirmation email from Zoho (with the subject “Welcome to Zoho“). If you do not find it in the Inbox, check in your SPAM/other folders. Alternatively, you can follow the steps mentioned at http://zohosso.wiki.zoho.com/#resendconfirmation to send the confirmation email again and activate your account with Zoho.
If you still have problems, please escalate it to support[at]zohoaccounts[dot]com.