I disagree that a problem with theory-A means theory-A is not "true." Our favorite theories: say relativity or QM have plenty of problems but we still work on them.

But your argument with Alexa is in my view in the wrong "direction." Alexa doesn't know what it means to be a light, and perhaps a computer "never" will.

But the real question is, how do humans "know what a light is", or what do you mean when you say a human knows what a light is.

My intuition is similar to yours, that our living in a "deep and complex" environment has something to do with it, but what?

The deep and complex environment might explain how we learn what a light is, but what is it? To put in Fodor's terms, what is the representation?

When you or I "think" (what is thinking?) of the light (what does it mean to think of the light?), what is going on in our heads?

I suspect whatever theory of representation you come up with will look something like a computational theory. The notion or concept of the light will be "stored" and have "relationships" and so forth.

edit: readability