If you are using The Observer XT 16 with a software-based license (and not a hardware license key), and receive the following message, please update The Observer XT 16 to the latest version, which you can find in the Downloads area of this site.
This message appears if the version of The Observer XT 16 you have installed is 16.0.1201. It was resolved in 16.0.1203. You can check the version of The Observer you have installed by going on the menu to Help > About The Observer.