The TSO trial that recently became available is put back. It was taken offline earlier, causing "server errors" when you were trying to download the trial. That's now been fixed. However, you now need a credit card to be able to play the trial. It won't be charged for the first 14 days, but you have to cancel the subscription within that period to prevent it getting charged. The reason Maxis has done this is because the trial was abused in some ways. People could easily get multiple trial serial numbers, resulting in neighborhoods ran by one or just a few people. That disturbed many players. It seems that now the credit card is verified so that there's no more than one trial account per credit card. Go right here to sign up and download the free trial. Note that it's a massive 1.2 Gb download, so broadband is highly recommended.