Hi AtlJimK,
Thanks for your question. Please try the following and let us know the outcome.
1. Make sure Terragen 4 is installed, licensed, and running properly on your computer.
2. Next, install Terragen Sky Early Access. It uses the same license file as Terragen 4.
3. If the problem persists, please open a command prompt, navigate to the folder where Terragen Sky was installed, and run the program from the command line. If Terragen Sky does not run, please let us know if there is any information displayed in the command line that might provide us with information as to why Terragen Sky is unable to run.