This error indicates a problem with V-Ray's interface license’s availability. If you receive this error, check the topics below, relevant to your license setup:
• Check if you have the license server installed. If the license server is working correctly, you should be able to see your licenses when you open an internet browser on the license server computer and navigate to its status page - http://localhost:30304
• If you use online licensing (obtain the license over the internet) you need to be logged in with your Chaos Group username/email address in the license server menu. Make sure you're using the username that's associated with your purchased license or a trial license. If you're logged in with the wrong username navigate to "Online licensing" button->Deactivate/ Sign Out to log off. To log in with the correct account click on "Online licensing" -> Enable / Sign In
• If you have your license on a hardware USB dongle, make sure the dongle is plugged in and the dongle drivers are installed
• If you obtain your V-Ray license from a license server on another computer, make sure your operating system's firewall or the firewall on the license server computer is not blocking TCP port 30304. You can test this by entering http://IP_Address:30304 in your browser, where "IP_Address" is the IP address of the computer with the license server installed. You should be able to access the status screen of the license server.
• Check your license settings. They should point to the computer with the V-Ray license server installed. Use "localhost" or "127.0.0.1" if that's the computer you're working on.
• If you share your license with your colleagues, make sure that the license is not already in use by someone else. Navigate in your browser to http://IP_Address:30304, where "IP_Address" is the IP address of the computer with the license server installed. Click on the box with the name of your license and check if there is a free license. You can see who is using the licenses by clicking on the blue number of engaged licenses.