Is the PC using an English language and the Mac using German? If so, it might not be able to address the property by name, because the string literals are different. You might have to address the property by number instead.
Assuming that the effect named "Text Color" is a color control effect: thisComp.layer("Controller").effect("Text Color")(1)
Found the solution. Expressions targeting effects are language sensitive! You need to start AE in english. You can do so by adding a empty textfile in your Home->Documents folder on Mac called "ae_force_english.txt"
You can rename every expression effect and attribute.