Thanks for your post! We apologize for the difficulty getting the Digital Viewer program to run. In our testing, the current version of macOS, Mojave 10.14.5, has no problem running the program, but will prompt about the need for an update for 64-bit compatibility. We are investigating a potential upgrade to the application with 64-bit functionality in time for the public release of 10.15 Catalina.
Could you please confirm if you have elected to try the macOS 10.15 Catalina beta? If you are using the beta, we would recommend using the Photo Booth application at this time. Again, we do a apologize for the trouble, and look forward to hearing back from you soon!