If you don’t understand the suggestions try Googling first
File not found
Make sure your Matlab path is set correctly
Trouble with MEX files
Make sure you have the latest version by downloading the working branch from GitHub: https://github.com/PaulFackler/CompEcon
I have no experience with MACs so I cannot help with specifics.
Issues with LOOKUP
MATLAB recently created a new Java function called LOOKUP that conflicts with the CompEcon function of the same name.
The CompEcon toolbox now uses a function called TABLOOKUP; download from the working branch from GitHub: https://github.com/PaulFackler/CompEcon