This probably means that you are behind a firewall or proxy that prevents Tasktop from contacting tasktop.com. If you have Tasktop Dev 2.3 or later, you can use your browser to manually download a license and import it into Tasktop:

• Open the Tasktop Account dialog: click the Tasktop Home <=> dropdown button in the toolbar within Tasktop Dev and select Account
• If you are unable to sign in due to a firewall or proxy, click "No Network Access?" at the bottom and follow the instructions in the wizard that opens.