I found a fix for anyone who has the same issue, its because Sim Update 15 change the version of the game and where its located.
We never suggested to put a path in the log file, precisely to prevent issues like this, because with no path:
logFile = Couatl.log
It will create it in its own folder in %appdata%\Virtuali
Or, if you want to be 100% sure it will never change, set it like this:
logFile = %appdata%\Virtuali\Couatl.LOG