The recent update to Mac OS 10.11 (El Capitan) causes our program to not display fonts. We have updated our software to correct this problem. You can download the updated app here: https://s3.amazonaws.com/simulearn-mac-assets/SimuLearnOS10.11.1.zip
Having downloaded the zip archive, extract it by double clicking on it and then drag and drop the new app into Applications/SimuLearn.
Restart the program.