I have visited their forum and found a message like this:

just got bad news here, Paypal keeps freezing Paypal-Accounts, and ours was frozen too right before. There were a huge amount of money in and we cant get access to our Account even if I mailed the Paypal Support and asked about my status. I also uploaded all the details, but nothing happens. Its not new, that Paypal freezes PTC ACcounts and keep the money in it.

So I agree that it is closed. Thanks smartkool for the information.
PLEASE DO NOT WASTE YOUR TIME ON BUXYBUX.COM