Looks like your account was closed due to inactivity.
As per the User Agreement
2. RESPONSIBILITY OF MEMBERS
If your account should go to inactive status (90 days with no logins), ClixSense will consider the account abandoned and close it. All funds in the account will be forfeited in the event the account is reopened. Any referrals or ad credits that are in your account when it's closed for inactivity will remain in the account.