Error with FPSController Standard Assets Script (freshly downloaded / imported)

It's been a few years since I've used Unity and now that I'm getting back into it, I'm having tons of problems I've never encountered before. Please help!

• I installed the latest version of Unity for Mac & imported the standard assets from the asset store.

• When I try to use the FPSController in my scene, I get the following error message: “The associated script can not be loaded. Please fix any compile errors and assign a valid script.” I haven't edited the script, so I'm really not sure what the problem is.