The problem is that if the customer is logged in as the root user, FG8 will not create the database. It’s a limitation (nominally a security feature) of PostgreSQL that it refuses to install as root. It can be installed by a user with administrative privileges, but not by the root user itself. Typically when the MacOS is installed, it prompts the user to create a non-root account to be used for day-to-day operations. The clue in the error log is the line pg_ctl: cannot be run as root.
The solution is to install Fitnessgram as a non-root user.